Interesting. I have a hard time getting invested in a PW that DOESN'T do a decent chunk of changes because the default rules are so broken in so many ways.
I didn't necessarily mean changes like scaling spell damage so casters progress as well, or editing classes like PDK or Harper scout to make them playable, or changing barbarian rage on a high-magic server to use AB/HP bonuses instead of useless stat bonuses bc you're already at the +12 cap, but when EVERY aspect of the game that could be customized is (e.g. 90% of the spells customized and not just scaling damage past 15 or 20 damage dice, only custom dieties with limited clerical domains, lots of feats modified, post-40 systems that are difficult to calculate, etc) that takes a lot of mental energy to keep straight, much less invest in the first place.
I'll give 2 examples, one from nwn and one from BG2.
For NWN, at The Awakening server, the post 40 system (up to 60) is handled fairly straight-forwardly - you get the same every other level progression of AB and saves and a general feat every 3 levels (no more bonus feats). Some spells are modified, but not a lot that I can't keep track or a quick check helps remind me. I know that a build that is 5 AB less at level 40 than another build will be 5 AB less (baring odd stat choices later) at lvl 60. Contrast that with Aventia3's post 40 system. The post 40 AB and damage scales based a multiplexed modifier from 0.25 to 1.0, based on your level mix at level 40. All of a sudden, builds that were powerhouses at level 40 like Blood and Faith (str based cleric 26 bard 4 RDD10) are weak at level 250 because clerics have a 0.5 modifier instead of 0.75-1.0 that true melee classes get. When you get to level 200, that makes a difference. It's also very hard to figure out how effective your character is going to be at level 100, 200, 400, etc, without getting into complicated formulas. Now I've played on Av3 and liked it, but now that I have 2 kids and am adopting a 3rd, I need my PWs to have tweaks and slight modifications to NWN, not a complete redo.
For BG2, like I mentioned in my other post, a mod like Ascension made the game harder by giving the bad guys 1. spell books that made sense 2. scripts that use them properly, and 3. most NPCs behaved like what they were, not just monsters with random powers. Contrasted with that the Tactics mod just made insanely powerful enemies, often lumped in groups, that had to be done in a specific order (e.g. get immunity item X to kill monster Y who dropped item A that let you then kill his buddy monster Z) to progress. OR Improved Anvil, which was a good mod, but it basically introduced new classes and items and turned the plot all around to the point where it didn't really resemble BG2 anymore.