I made all races playable + meph's work! Here's how I did it:
1. Install All Races Playable & WinMerge
3. Use WinMerge in tandem with the 3 files All Races Playable alters to change anything non-graphics related in the raw files. (any sprite graphics and/or stat edits are to be left alone. Only change properties such as playable, trainable, etc, which are typically done on animals or the 4 main races.
4. Go to the entity_blank file you want to play
5. You will see many !NO_FORT_MODE_(your race)! markers. Replace all of these with a left bracket ("[")
6.At the top, just below the Entity:(Biome), add these:
YES_FORT_MODE_(your race)[SITE_CONTROLLABLE]
YES_ADV_MODE_(your race)[ALL_MAIN_POPS_CONTROLLABLE]
It should work now! Make sure you don't add (your race) and instead your actual race (HUMAN, GOBLIN, ELF, etc) I'm only trusting this to work on accepted & fundamental races w/ civilizations like Goblins, Elves, & Humans, but feel free to try it [on a blank install of Meph's]. I was surprised how easy this was when I was fiddling around in the files. I'll be sure to update this if I encounter any other problems that need fixing as well as how to fix them, but for the moment, this works pretty well in my experience!
Sidenote: This won't work on an already started fortress. Abandon it & then reclaim to have the changes take effect.