This turned off-topic quick, nobody bothers to read the OP these days? I'm specifically talking about the ability to cancel an ubercharge mid-charge by picking up another medigun and then picking up your own medigun again keeping whatever uber% was in it when you dropped it mid-charge. Also Valve should remove the cheat flag from tf_dropped_weapon_lifetime so normal server cfgs can change this (eg ultido can easily ban medigun pickups). Or ask AnAkkk to do it inside tftrue since everyone has that plugin anyway.

[...] And a medic can reduce this risk even more by switching weapons if he gets pressured/bombed/whatever.

[...] But you still have 8 seconds (or less, depends if you were forced to flash as well) to pick up the other medigun to make any use of it. Also it would be quite dangerous to not have uber on you in case the bomber(s) haven't died yet. I could see it may have a use in Viaduct perhaps, but on other maps the distances are too long. Also, the other medigun might just have more uber anyway. E: Now that I think about it, I could see it as a potential way to bait the bomber on to you if you are just sitting next to the enemy medigun.

[...] But that scenario happens every time you kill the med and have uber. And even more so on viaduct. You always have aggression onto you once their med dies.

I think it's super rare that you happen to find an enemy medi gun as you are popping and not wanting to use it fully after all. Basically your scenario is the only way this could happen.