I've done a little bit of testings on sandbox for these medical nanobots...I think the way they work and how they can be upgraded is something that should be rethought.

First, I think that having them spawn directly upon craft from a Molecular Forge is alright on its own, but maybe having a way to transport them around once they're crafted before deploying them could be more practical if you ever wish to send them into a specific place, like a sealed room for example. Think of putting them into a canister of air, and releasing them from a Canister Emptier.

As for them hanging around in the air, a problem I notice too often is that they just die from overpopulation in oxygen, until a point where there isn't enough per tile and just trigger the "Dying off" factor, which isn't great if you're looking to give your duplicants the bonuses they provide should they be upgraded, because most of the time they don't trigger the bonuses even at lvl 15 in Exposure Threshold within tiles of 40k nanobots.

The bonuses they grant to duplicants are really good, at max levels they grant:
-45% stress/cycle (-3% per level)
+500 kcal/cycle (+33.333 per level)
+45% stamina/cycle (+3% per level)
+4.5 germ resistance (+0.3 per level)
+15 to all attributes (+1 per level, which IMO is stupidly powerful)
+2% breath /s (they can just hold their breath infinitely)
+900 health/cycle (+60 per level)

Personally, the only ones that could be changed would be the stress reduction and the health regeneration. -45%/cycle is quite a lot, it's not as efficient as a massage clinic, but it doesn't cost any power and it doesn't prevent dupes from doing their tasks and such. Maybe it should be tuned down to -30%.
The health regeneration however is just ridiculous. I've spawned a dupe within a 1x2 enclosed room full of magma, gave him the nanobots boost and he'd be like "NANOMACHINES, SON!"...well, it wouldn't fully heal him, but he lasted a good minute in that magma before being incapacitated. Now there's a duplicant roaming around the base who's 650 °C hot. Sooo, I'd say it should be lowered down, like REAL down. Maybe 150/cycle should be the max for health regeneration.

Now, there's a big problem I'd like to cover though, it'd be the costs to deploy and to upgrade the nanobots. If there was one way for me to describe it, it would be this way: https://youtu.be/WfjHbpXt-oQ?t=6
The price to release the nanobots? 10 tons of steel!
And to upgrade them by one level? 10 tons of steel and 10 tons of common materials, or 1 ton for rarer ones!
Could you imagine how much time it would require just to go from lvl 0 to 15 for a single type of upgrade, and how much it would require in materials? There's no way anyone would be able to reach that before the 500th cycle, or beyond even, not without mods at least.

Some of the upgrades don't seem to work at all, the Leaden Coating doesn't seem to make any difference. I've reached lvl 15 for rad protection, and now the radiation kill rate shows -2.235174E-08...so I'm not sure if it's meant to say that it now multiplies in radiations since it's a negative number, or if it's supposed to be a flat 0. But either way, putting them next to heavy radiations seems to just kill them whatsoever.
The Operative Optimization upgrade gives the equivalent of the ImmunoBoost Protocol rather than the extended duration like intended, which means it cannot upgrade the duration of the bonuses.
The Integration Protocol doesn't trigger the bonuses even in high numbers, they need to be in VERY high numbers to actually trigger them (like I said above, with the 40k per tile not triggering the bonuses at lvl 15).
The Insulation Coating doesn't prevent them from dying in less than half a cycle within a 8x5 enclosed room full of oxygen, for 1000g of oxygen and 1 million nanobots per tile in the room at 27°C for their supposed tolerance of -65 °C to 105 °C.
The Perpetum Mobile Protocol still doesn't prevent the overpopulated factor from triggering, and it doesn't mitigate the loss either, it still shows as -13% dead/cycle.

So yeah, there's still a lot to rework about them little bots. The idea to have nanobots so they can enhance and protect your dupes, is an idea that I welcome with open arms, but the way it's made right now, it leaves quite a lot to be desired.