UMP45 Mod – ★★★★★ Submachine Gun
Tags: Class: Submachine Gun Misc: Digimind Upgrade Role: Debuff Tank Skill: Smoke Skill: Unique Team: 404 Tile: Buff Crit% Tile: Buff FP
So if it hasn't been said enough, absolutely get the Mod1 the very second you can. It's 200 fragments and some cores for a fair boost in performance. Extra stats, a bit more FP buff on her tiles, a little extra HP, and an improvement to the slowdown effect on the smoke.
The real problem is her 2nd skill is janky and not extremely practical. It's a little bit of a bonus, but not likely to make or break a fight. So yeah, the Mod2 isn't great. The mod 3 however, gives her a unique equipment that goes in the suppressor slot and is basically a suppressor with better stats (+5 EVA over normal) which helps her tanking ability somewhat. Whether this is worth it up to you, but definitely get the Mod1 at least.
The rest of this is basically the same song and dance where she has top class offensive buffs that continue to remain unmatched among SMGs, so you WILL likely continue to use her.
Like many mod skills, UMP45's is jank and works funnily. For 1, the debuff remains even if 45 leaves the field. The biggest weirdness however is that the damage effect will go through anything, including invulnerability via shields. So yes, you too can have tiny chip damage and kill anything eventually if you can keep your dolls alive for that long.