Kevin Love cannot play center even in small ball lineups, that is the point of them trading for Frye. Rather than having Tristan or Love at the 5, they can go with Frye which will pull the opposing big man from the rim and allow LeBron to play PF with 3 shooters on the floor to space it.
This isn't a glamorous trade, but if you've watched the Cavs in the past they have played James Jones at the small ball 5 just for spacing, Frye is still 6'11" 255lbs and can be used in a lot of different ways. It gives them flexibility to throw out a lot of different lineups that they haven't been able to try because Love doesn't have the length to defend while Mozgov & Tristan cannot shoot from the outside.