Crosmando: Are you kidding, day/night was very important because all the nasty monsters came out at night, early in the game this was a big deal and added challenge, not to mention it added so much atmosphere.
Also, glad you mentioned Spell Points regen, because BT4 also did away with that entirely, there's no resource management angle of you having to be careful about how many spells you use while in dungeons (so you don't blow them all too early). Roscoe now only sells items, there's no spell points to buy.
The day/night cycle only mattered early in the game.
Also, in 8-bit versions of BT3, Harmonic Gems were really common, so you could easily restore your SP anytime it's necessary. Add in a couple staves that cut SP cost in half (one of which is found in previous games, the other one is not), and SP isn't an issue in BT3. (In 16-bit BT3, Harmonic Gems are much rarer, but those versions have so many other bugs that I don't consider them to be representative of how the game is meant to work.)
It's also worth mentioning that, in BT1, by the later part of the game you have lots of SP, and there are no spells with high SP cost (even the spell that fully heals the entire party costs a measly 12 SP), so SP becomes a non-issue toward the end of the game. (BT2 has a few spells that are expensive enough to be a problem, including the dreamspell that costs 100 SP, but is really powerful.)
I would rather have Roscoe selling items than have a situation like BT3, where there is *nobody* who will sell you items (well, except drinks from a tavern, but there's a weapon available early that makes them obsolete).
Crosmando: But the question is; if you have the opportunity why not make the sequel more complex and add more character customization, which is certainly in the spirit of 80's and 90's CRPGs.
More complexity isn't always good. Consider that Daggerfall was probably too complex for its own good; Bethesda was right to simplify things for Morrowind. (Of course, Morrowind's level up system is an abomination with perverse consequences; skills increasing on their own works well (aside from the fact that it takes too long to reach high skill levels), but the way level up stat growth works is not that good.)
Crosmando: And even so, attributes still did things in the originals.
Except that:
* In BT1 and BT2, attributes only matter past 15. In BT3, I believe a score of 15 gives a small bonus (the same as 16), but anything less is still the same.
* In BT3, the stat cap is 30, but there's no difference between 26 and 30.
* Also, the to-hit and saving throw mechanics are broken in BT2, and to-hit is broken in BT1 (at least in the DOS versions). After a while, enemies can't hit you until the final dungeon. In BT2, except for beginning characters, your characters can't be hit by enemy spells (enemies can (and do) bombard your party with Mangar's Mallet spells (wouldn't it be nice to have one in your party?), but they never work.) From what I have read, in the Commodore 64 version of BT2, after a certain point your characters can't hit the enemies with physical attacks, at least not without major magical assistance.
By the way, one funny bug in the DOS version of BT2: Anti-magic zones prevent regular spell casting from party members, and prevent enemies from casting spells or using ranged weapons, but that's all they do. A monster in the party can still cast spells and have them work. Meanwhile, an enemy might throw a spear at one of your characters and have it fizzle. (Does that make any sense?)