I thought you said she was good for mid-game. You mentioned save-editing for better suits, but since that wouldn't put Darwin on the map, I'm not sure how that would help.
Late EDIT: It's possible to have Vargas put Darwin on the map by giving him Hell Razor's journal, which can apparently be done before being allowed into the citadel. So I guess you can have Pizepi even for the early game. And ammo wouldn't be an issue if you pick up VAX before Ag Center and Highpool. Either because of constantly Cyber Scrounging VAX, or because VAX mercilessly kills all humans.
No. I've only seen people mention it when they ask for more combat options. I don't know why other developers don't shamelessly copy everything about it if it's so damn good. Maybe it would interfere with RPG aspects and levelling, which people also seem to love? Personally I don't care much for more combat options. Playing first person shooters where I have to use extra keys to lean out from behind a corner is just annoying. I grew up playing games with a joystick and never learned how to use a gamepad. Buttons here, buttons there, buttons everywhere. Maybe I'd like Jagged Alliance 2 if I tried it, but I haven't made an effort to get hold of a copy.
Options don't have to be bad, but they frequently end up that way when the players start to investigate which builds are the best for DPS. Balancing everything might take a lot more effort than developers are willing to put in. Maybe it takes skill as well, and developers frequently lack that skill, and players frequently don't care enough to weed out the developers who make unbalanced games? If everyone were like you, there would be nothing but games for you, I'm sure. You and everyone just like you would all vote with your wallets and win the entire market share.
EDIT: It also occurs to me that one of the reasons I don't like having too many combat options is that the developers have to teach the AI to use those options effectively, or otherwise it's like giving players unfair advantages that then usually are countered with the AI simply cheating somehow. Sometimes less is more.