Please "read my lips", not saying this any more
--> Flooding the used market with "enough" of "suitable" aircraft "all times" is not going to happen. There is, and will be, certain amount
of used planes available all the times (and the number of aircraft made is also balanced to reflect what has been produced in the reality) - the system takes care of this. Why you then keep seeing those E110's and other small ones there "all the time" - that's because the "good ones" are sold very fast and other planes stay on the list longer (but they too are rotated and after some time disappear..).
But if the demand of aircraft is very high (like at the starting phases) it is not possible to start dumping hundreds and hundreds of extra aircraft just because they are needed. When the demand for aircraft is high, there is always a shortage of the most popular models, no matter what is done. And this, finding the proper strategy, is part of the play. You cannot expect to be able to grow at all times without any challenges on the way, was the concern then routes or aircraft.
I am planning to introduce for example staff market and availability concepts too. So just getting the plane and route is not enough, you need staff too - and qualified pilots for example may not always be there for you 24/7 to hire.... Of course part of the problem is that players spending more time are able to scout perhaps better deals on the market, but there is no solution for this - some "aircraft agents" wouldn't really be helpful as everyone would still fight for the same A320s and so on.
This said, there are still some minor changes coming (like the time when planes are put to market by brokers, and possibly one bigger change concerning new airlines (with other new features too) - but those will be announced separately). But the there will be NO major changes otherwise.
btw. at the moment I do see on the list A300, 2x ATR, RJ100, 727, 737-200, J31, J41, lots E120s, lots F50s, lots F28s, lots HS748s, DC-9, lots S340s .. all which I could take to my airline, if I'd have one. But finding an A320 on the used market .. good luck
So saying again, that think outside the box - there are others than Boeing and Airbus.