That would instantly eliminate the unfair bots arguement besides AI behaviour which is a seperate issue.

Yes it could get bored or even irritating quickly when your bot won't ever use any other good mechs, weapons etc., but personally speaking I don't trust my bot at all to have consistently good builds if that's the tradeoff. I would take never hiding behind another Bastion, pushing with Surge etc. ever again. 

The second argument I could understand is the unfairnes if your hangar is even 5% weaker than theirs and their power is virutally doubled, but i'd argue that's the exception when 90-95% of players have horrible bot builds in at least one round every single game.

Even if i granted the weak hangar stance, by definition you shouldn't be playing in that league if you know your hangar is on the weaker end which is unfair for your own teammate. Many, many players do this and wonder why they lose so this will immediately expose bad faith players.