Since you cannot build a colony on an Asteroid Belt, removing any resource gathering from Outposts makes Asteroid Mining, and the improved version, completely worthless techs.
Yes, if that were to happen, that tech would simply be removed.
I think asteroid mining is very flavorful and beloved by lots of players.
If that gets too complicated, then you could, for example, have this:
When you get Environmental Encapsulation, you can build Outpost Modules. When you get Asteroid Mining, you can build Mining Outpost Modules, which are a different beastie all together, and allows mining on that outpost. Other techs would make Farming Outpost Modules, Research Outpost modules, and Industry Outpost Modules. Actually, since Industry is a factor of population, just skip that one entirely.
This would just delay the problem that players are urged to send outposts everywhere.
I totally agree with the first post of eleazar about the implementation of outposts, but would love to see mining outposts (or advanced outposts or whatever they should be named) that can only be build on objects that cannot have colonies (Asteroids and later Gas Giants). Mining outposts should do everything a normal outpost does plus generate ressources.