The issue here is following: Villa will most likely leave whether we like it or not. I sincerely believe that he still has enough desire in him to play as a starter instead of warming the bench. I can see him leaving.
What comes to selling Alexis now - I do understand where you come from in terms of his price possibly decreasing further if he will be kept on. In that sense, it would indeed make sense of cashing on him now than in, say, year's time. However, the issue I have with this is that we somehow expect Deulofeu hit the ground running from the get-go and there's no guarantee his first season of integration will be a smooth ride in terms of added value + end product.
Pedro is more or less an equivalent to Alexis here, and IF he'll get his motor humming again the same way he did a few years back, I don't see any reasons for us not to sell Alexis. However, it is once again a huge IF and Pedro has been incredibly passive over the past few years, so the signs aren't overly promising. In addition to this, there is no visible added value here.
Tello on the right, on the other hand, seems quite a plausible option given he has had an equally productive time on both flanks. Kudos for bringing him up, as I've actually completely forgotten his contribution over the right side.
However, despite of having Tello and Pedro who can both play on both sides of the pitch, losing two forwards will most likely end up hurting us more than it will do us any good. Yes, there's a possibility of adding both Neymar and Deulofeu to the roster, but having those two for Villa & Alexis will not necessarily add up. These, of course, are my personal opinions and I may as well be wrong on Deulofeu's impact. However, given the fact that some of the players mentioned over Alexis are widely inconsistent and relatively inexperienced hardly adds any force to your argument.
Besides, shouldn't we be striving to replace Alexis with a proven player given he leaves? In addition to that, back to my initial question, what other relatively cheap hybrid 9 / RW's are there on the market at the moment?