Changes needed:
Earlier access to the Valkyrie and Zenmaster classes, this is what the designers originally intended.
Fixing the bugs that stop access to some of the Brimloch Roon quests. See Page 9 of the Best Tips found at Ironworks Forum.
Fixing the need for each PC to get a Letter of Jathil&&&
Support for modern monitor sizes.

If Gog can fix these issues, we won't need to use workarounds.

Hotfix 1 doesn't work for me - deep6.exe error.
This is no complaint or request for help: The reason is very likely that I'm using the unofficial patch 1.0, the Town AVI fix and Ludmeister's Mod, which means the deep6.exe is different from the one GOG uses.
I have also never suffered from the mouse lag or the Gareth encounter problem mentioned in GOG's change log.

My question is: What is the relationship between the GOG hotfixes and the unofficial patches / mods I'm using? Is there a reason to prefer the current GOG version over my personal installation (except that I'll never been able to install GOG patches as long as I don't uninstall my patches)? Let me add that I do like the modifications of Ludmeister's Mod, which improve the role-playing experience for me.
And does anyone know if Ludmeister's Mod can be installed after and is compatible with the 2 recent hotfixes?

In case someone is interested:
- The unofficial patch 1.0 is from Heuristic Park (developer of W&W) and "provides numerous bugfixes that were present in the commercially licensed version by Activision". I still don't know if GOG is using this patch, but it's applicable to the GOG version, so the answer is possibly no.
- The Town AVI fix was created by Ludmeister who "rendered the town AVIs using VirtualDub v1.6.15. They replace the game’s original town AVI files, to restore full functionality to towns when running the game in Windows XP."
I had this problem in the past, and the fix solved it perfectly.
- Ludmeister's Mod "changes slightly the skills and magic books that some classes open, and makes level ups a bit more helpful, skill-wise. It modifies the items, weapons, and armor in the game, as well as the treasure drops. Many items are now stackable that weren’t, and almost all non-quest related weapons and armor are enchantable. It also removes the infamous "smite party now" attack that Amazoni Mantraps and Jungle Lilies had."
(for details see http://www.jeffludwig.com/wizardswarriors/download.php)

the unofficial 1.0 patch is applied to the gog version as the patch files from jeff ludwigs site are present in the gog install dir, and since it was just a unzip and overwrite files type of thing, the two readmes are also present, as for ludemeisters mod...I dont know if it will work, just try backing up the deep6.exe before installing, or just adding the data files and overwriting.

I just downloaded W&W 1.0b hotfix from GOG and compared the files with my older installation.
Yes, the unofficial patch 1.0 is there now, but not Jeff Ludwig's 2 mods, townavi and Ludmeister's mod. Townavi is not really required unless you have difficulties in towns, and Ludmeister's mod changes a few game properties, so it's a matter of like it or not.
This answers my question. Thanks!