Find him a Tag Team partner or Stable partners
The Tag team division is seeing big improvements these days. There have been a plethora of teams flown into the mix and the division could use the addition of a foreign heel team as well. All WWE needs to do is find Rusev a partner.
Getting someone from the main roster or picking from NXT would do the work just like the valet situation. On the main roster, they could just build a stable of Foreign Heels around him with the likes of King Barrett and Sheamus. Having a stable is a brilliant idea for the roster as the fans would really love to see some stable wars like back in the Attitude Era.
As far as NXT is concerned, Baron Corbin, Bull Dempsey or even Rhyno could make a good partner for Rusev.
Let him join the Authority
The Authority is where all the big heels belong to. They have been reigning as the top feel faction in WWE for nearly two years now and they are really losing the steam right now. The likes of Big Show and Kane are not getting the work done as henchmen. There is a certain need of new recruits there and they could do wonders with Rusev.
Rusev walking along with Stephanie McMahon and Triple H will certain raise his stock and at the same time it will keep them near the main event scene. After a long time, Rusev could just turn on Hunter and then have a face run, similar to the one that Batista had a long back.