So u want a autohost with "!maxplayers 10" - should be possible.
Get a PC not made out of potatofrags.
Get a Internet connection not made of Bamboo.
Get a Server that can handle it. (maybe a virtual server 4 15€/Mounth)
Get a game/engine that uses more than 1-2 cores of the clients PCs! (sadly (not) possible and asked 2 much - i know)
The reason why small team games aint that popular? cuz u have to do everything yourself! Grid, AA, Anti, SpecOps, Basic defence and Microing.
In the big team games everyone kinda got its task and u can focuss on the gameplay or microing ur units more whats more fun!
And YES there still do exist peeps who dont bulid any defence at their factory and wonder why it got destroyed in minute 3 if they aint aleready asking why/how their com got lanced at front. The difference in small team is that its 1/5 or 1/10 of the players whos facing temporary game over if that happens (also the eco lose on small maps where every com matters). In big Team games its 1/10+, 1/16 or even 1/30! (Yes ive played kinda 30 vs 30 before dunno if it were exactly 60 but 50+ fore sure! Worked fine on my PC and i LOVED it! Yes there were sometime little lags which wouldnt happen if zero-k would use all/more of my 8 4,5 ghz cores!)
Decreasing the metal? Hell no! Then ull have ur 5 units and thats it. Itll also shift the community behaviour to the worse! (Saving/rescuing allied units? - no i want the reclaim). Also the game will become a scynthe only game.
Shared units aleready exists! It can work suprisingly well or end up in a toxic saltmine.
To the map size im against it. There small maps playable with large Teams. And there Huge maps playable with 5 Players.
But there also maps which are no fun without a certain amout of players.