Well, there is a *REALLY* big issue I have with the non-Skywalker (or non-Solo) theory. SW:TFA made a pretty big deal out of the Skywalker Lightsaber. When they got to Maz's place, there is no question whatsoever that it was the Skywalker saber that was calling to Rey.
And then there's all the stuff Maz said to Rey to try and get her to take it and how she (Rey) knew the truth deep down. But Rey was totally freaked out by the effect that the Skywalker saber had on her and what *it* was trying to tell her. Also, the Skywalker saber obeyed Rey's command over Kylo Ren's. If Rey is not a Skywalker, how is it that the Skywalker saber "listened" to a non-Skywalker over an actual Skywalker(Solo)? Kylo/Ben even said "...that lightsaber is mine!"
Obi-Wan in ANH even said to Luke "...your father wanted you to have this when you were old enough..." SW:TFA seems to be carrying that idea another step further. Sort of inferring that the Skywalker saber has been (for lack of a better word) enchanted by the Force via it's connection to the Skywalker bloodline. Almost in some respects akin to in LotR how the "One Ring" was bound to Sauron and had a will to return to it's master.