I hope not, that would be a terribly unintuitive and a bad system. I like retroactive growth systems the most, as it doesn't force you to chase HP like in Morrowind/Oblivion, or re-roll like in BG.

If I do design an RPG that meets the criteria I mention in the first post, HP gains will be retroactive, or (equivalently) HP will be a derived stat computer from Level and Vitality, with the only other factor being any passive stills or magical effects active on the character (like how Final Fantasy 5 does it).

(This is one thing that FF5 gets right that FF3 gets wrong; in FF3, HP gains are based off vitality at the time of level up (and vitality is affected by job, making it a bad idea to level up while the character is a Scholar, discouraging the use of that job as using it temporarily will hurt you permanently), while in FF5, your HP will adjust on every job change (so spending time as a bard won't hurt your HP in the long run; you'll just have low HP until you switch to a job with more vitality).)

Interestingly, I don't mind the classic Wizardry approach, provided that the game doesn't limit the number of level ups or provides a way to level down: Whenever you level up, the game re-rolls your HP for every level, adds the Vitality modifier for every level, and gives you the total if it's higher than the old value. (If it isn't higher, you gain 1 HP instead; in some versions (console versions mainly), if that point would result in integer overflow (unlikely in normal play; you would need to have 32767 HP before leveling), the game doesn't give you that point.) This means that if you get a lot of 1 HP levels, you're bound to get a lucky level up soon. (It also keeps class changed characters from getting too many HP, an issue that affects Bard's Tale 1-3 and some Japanese Wizardries (including Labyrinth of Lost Souls, though that game does halve HP on class change just like Dragon Quest 3).)

Yeah, that does sound nice.

Speaking of skills, which DRPG and JRPG that you've played would you say has the largest amount of skills to pick from? Not just at character creation, but during levelups/skillups too? Not meant to go too much off-topic, but just curious. Some games have passive skills like +20% HP, like in FFV, are you thinking of using that, and if yes, will you need to slot passive skills, or will they stack, just like in FFV? So after learning it, you have it for all classes/your build?

Edit: Whoops, you did mention the passive abilities from FFV. So it will be just like there, and not FFTA where you have to equip them, right?

I can't think of what game would have the largest amount of skills to pick from, as I don't pay too much attention. In some cases, particularly when skills have values that can be increased (whether through use, skill points, or something like ability points that's separate from XP), having too many skills can make things too unwieldy. (Final Fantasy 2 should have had some skills grouped together; Secret of Evermore has this issue, where you might get a weapon or spell upgrade, but the new weapon or spell starts at level 1 (or 0).)

It would probably be like FF5, where you have to equip an ability like HP +20% for it to be active. On the other hand, I will probably take a different route for the Freelancer job. (One idea I have is that Freelancers would gain stats FF2 style, when every other job would have fixed stats based on their job. Freelancers would start weak and possibly get quite powerful, but other jobs would be powerful enough that players wouldn't need to use the freelancer job to beat the game's hardest challenges.)

As for the RPG I'm actually thinking of making, I haven't thought about passives like HP +20%. With that said, the game wouldn't have levels (or an equivalent concept) at all, and therefore would not meet the criteria for this topic.

I like having tons of skills, so whenever I see a large selection, or lots of jobs+skills, I remember that. :)

If there is no level-growth, what will you scale attributes off? Physical+magic skills for the corresponding attributes?

It's worth looking into how some of the SaGa games did this:
* Romancing SaGa: Minstrel Song: Your chance of attribute growth is based off the character's growth rate in that attribute and the action being performed. A stat can increase if no action boosting it is performed, provided the character's growth rate isn't zero (in which case you do have to perform an action related to the attribute). Skill levels don't increase through combat, but are instead increased by spending gems.
* Romancing SaGa 3: Skill levels increase through use, but attributes do not increase at all; they're fixed for every character (barring events that might change them, but they're rare).
* SaGa Frontier: There are no skill levels. For humans, attributes increase based on actions; other races have different ways to boost their attributes.
* SaGa Frontier 2: There are no attributes (except HP/WP/SP/LP); there are only skills which increase by use.
* SaGa 3 remake: Attributes increase based off actions, and there are skill levels that can increase as well. Note that some races get significant portions of their stats from sources other than their base stats. Also, note that each (non-monster) race can only increase two weapon skills (except humans, but their other skills increase at 1/6 the rate), only espers can increase magic skills, and that a character's race will usually change if the character eats meat or installs parts.
* The Alliance Alive: Attributes (other than HP/SP) don't increase. Each individual art has its own position levels, which can improve when you use the art in the specific position.

For the RPG I'm thinking of making, I'm thinking the stat growth will be like SaGa Frontier, although I have different ideas for esper and monster stat growth.

How is this ever a desirable mechanic? Anything that makes players hold on to their upgrades till the very end of the game sounds like bad design to me?

You misread my post here. I'm asking gave developers to make it so that, in the long run, it shouldn't matter when you raise your Vitality (or whatever the stat is called).

Ah, the famous "55 Monk" build. I see you're a man of culture as well. :-)

Reminds me of the HP situation in Dragon Wars. What's worth noting about it is the following:
* Health is expensive; one HP costs 2 skill points, which is a full level's worth. (Combat and magic skills have the same cost (except fistfighting, which is 1, and learning a new magic skill, which is 5 or 10.)
* Bandage (2 SP per point, just like Health) can heal a character, but only up to 10 + its level (so Bandage 2 heals you up to 12).
* Then there's stun, which starts each battle at the character's max health. Attacks that do health damage do double that to stun.
* A character with 0 stun is stunned; said characters can't act, but can be revived with a healing spell or the end of combat. While stunned, the character won't be targeted by enemies and will be immune to all damage.
* A character with 0 health is dead, which can only be cured by going to a specific out-of-the-way location. (Usually, a death means a reload in this game.)
* As a result, a character with higher max health but the same current health is more likely to run out of health before stun, and that's not good, as death is more severe than stunning. Hence, higher max health is not good, as it puts the character at risk unless you use healing magic (as opposed to just Bandage).

I could also mention the original Zelda, which has this quirk:
* At full health, you can shoot sword beams, which allows you to hit enemies on the other side of the screen with your sword. (Otherwise, the sword's range is only about 1 tile.)
* You start the game with 3 hearths of life, both current and maximum. This gives you sword beams right away.
* If you continue after death or reload a save, you start with only 3 hearts of current health. If you've collected at least one heart container, then you do not get sword beams.

(Another interesting case is Undertale, where higher current HP means you take more damage, though higher max HP isn't strictly bad in and of itself.)