I like the idea of having moderators with the above suggestion
also all assets should be put into their own version and if the Devs do not give support then they should be removed to a different part of marketplace possible labeled not supported
i have bought may new assets where the developer never answered emails and at my level it is lost money to me if i knew there was no support i would not buy.
as mentioned you could have multi star rating
E.G
content *****
quality *****
Support *****
Updates *****
I still concider my self new to unreal engine so the extra info would give better choices when buying