also you can bring an training ground like, where if you want you can let an wave training (obviously it brings up the problem of this wave don't advacing while the enemies one are coming), with an limit of "training time", but when you choose then to come into the lane, or when the limit is reached, they will go to batlle with time and class respective bonus.
This can be also an way of control the random thing. Or get better results of captain spawn.
You can add some temporary buildings, that costs resources both to build and to maintain, like and "rifleman nest" that shoots the enemies comming and give some extra sight range. Or improvised tower , barricades or any defence like build, so if you had a bad start and lose some buildings, it don't mean that now when you are stronger you will cannot keep your defence lines.
The idea of some very " unusual" playing heros could be good.
Like a ghost one that do little difference alone, but he can temporaly meld itself with other players heros to boost their stats. Or it can create "creep melding spirits" that fuse with creeps.
or a creep turned one ( yeah i feel a big lack of creep support in most maps)
that add aura effects and buffs only to creeps. like the captains idea, but obviouly with all the hero advantages.
Also an counter based hero, turned only to repel effects making it coming back to their casters and some other minor functions.
OR this is a damn different one.
and base administrator hero, little use on the lane, but in the base it have a lot of funtions, and gains EXP by combat and by this base management, where he can increase the chances of some effects repair structures or make better creeps and so on.