You have some interesting points. However, I think you are missing an important aspect of having Ellis, Loe, and WR on the floor together. When Loe and Ellis are on the floor (with WR), Ellis will have a mismatch against most 3's that are forced to guard him. Therefore, when Loe is on the perimeter and a 4/5 has to step outside to guard him, it opens up Ellis to post up his man. Also, if the other team switches the guarding assignments between Loe and Ellis, then Loe can go inside on an obvious mismatch. At the same time, both Loe and Ellis will have a size mismatch on the outside against whoever is guarding them and may be able to shoot over the top. One other thing to note, Loe has shown a consistent and impressive ability to drive that few 4/5 players are going to be able to stop, which could leave mismatches on the inside, or open shots on the collapsed defense.
The effect may be that most teams are forced to play a zone against us, which plays right into the hands of a team with some slashers (KM, KC, and potentially MM) and some solid exterior shooting (CE, RL, JJ, KM).
Defensively, I am not worried about Ellis guarding a 3, he seemed surprisingly quick for player of his size. His physique reminded me of Luke Walton, who I believe plays the 3. He just needs to get better conditioned and more toned down.
(Also, as a side note, don't forget that JS can guard the 3 pretty well. If he develops, he could add another dimension to this team)
Any way you stack it up, this team has the potential to be really exciting next year.