Agree with the OP on the fundamental premise: Celtics are probably encouraging Kanter to extend his range, ala Lopez, or for that matter, Horford.
Strongly disagree on Kevin Love. That would be one heck of a defensive frontcourt pairing (not in a good way).
I like the Lopez comparison, assuming Kanter can become reliable out to 3. That's because you can pop him all the way out in the pick and roll, or try and punish defenders down low if that's what the matchup dictates.
Keep in mind that Lopez also had a reputation as a horrible defender before he got to Milwaukee. Budenholzer essentially gave up on him chasing guys out on the perimeter in the pick and roll. That turned out to be a weakness of the team's defense, but hey, they still won 60+ games and schemed around the problem in the playoffs. It would be great if Kanter turned into the same type of deal.