The server will lose money, more servers will have to be created to hold the players in the unranked ladder, as many people would play on it. The non-donors would play here which would mean that the unranked ladder would exceed 50 players at any given time. Have you ever seen "Out of arenas at the moment, try again"? This is exactly the reason this happens. There are simply not enough arenas to hold the players in. Also, yes, Build UHC is one of the most popular kits on Arena, and making it unranked would mean that people wouldn't buy ranks to play on the servers. This is not Pay-To-Play, this is just giving donators perks which non-donors can get a taste of (with limited ranked matches) and adding Build UHC to unranked would overrule this completely. See it as a free app on the App Store (or Google Play for you Androiders). There is usually a free version and a paid version. The free version gives you a taster of what the paid version would be like, so that you would then proceed to either buy the full game, or not decide to spend money on it. Simple how it works really. Anyway, that's just how I see it xD