As a frequent borg and drone player, I agree that they could use some spicing up. My thoughts.
For the heavy / light / etc frames, I like this. I remember in much older times, you could adjust how hardy a borg would be while making the bits and pieces by welding stuff to the parts as they came out of the fabricator. The same sort of concept could be applied here, if not just making the exosuit fab gain new borg part recipes via science. Back then, the armor didn't slow you down, so it's only fair that it would, like you said. Or if people don't think that's enough, it could have other affects - more armor makes item cooldowns take longer, and wears the battery down faster (since it takes more energy to move) etc. Frankly I wouldn't adjust the timers for the light borgs, being fast seems good enough there.
The AI interface board seems cool. But does that mean that the AI would just leave the borg in a charger while busy doing non-cyborg stuff? Does the borg only work where cameras work? What happens if you emag it? Is it restricted on what modules it can pick?
Upgrades: I know antags will be afraid of the Recovery upgrade, so a lot of people are gonna want to know how that works. How fast do the borgs recover once they try to use it? Is it possible to neutralize this, short of your battery running out? The Teleporter upgrade is extremely useful, I presume they still have to calibrate it to not teleport to space.. but what prevents emagged borgs from just rushing into telecoms and the bridge with this? Granted it's not like it's hard for a borg to just quietly break into the teleporter room and do these things, but unless there's a downside, I dunno about this one.
Engieborgs: On other stations you could build pipe segments with the RCD. It's fine if that's not how it works here, but engieborgs desperately need to be able to fix pipes. Humans lose the dang pipe maker way too often, like you said, nobody fixes atmos because of this. I can understand drones not having this, but borgs need it. As for plasteel / plasma, I agree it's nice to be able to fix stuff like toxins and the ai sat back to how they used to be. I only think they can't do that now so it's harder for borgs to effectively block off access to stuff (although there's plenty of other ways to make a room nigh inaccessable)
Secborgs: Personally I think a taser would be better than the disabler. I mean, you could keep both, to be able to still shoot through windows, but hey. And honestly, what fun is security without pepper spray? Honestly, it's a good way to stop the ever-so-common crew fights without literally shooting / prodding someone. Make it so it only refills at station / while charging if you need to, but I like this.
I see no problems with the other borg upgrades. Maybe people will think it's silly to make standard borgs slightly (barely) more useful, but hey.
At least we aren't trying to get replicants back. Nobody wants that. Just no.