Just one more comment regarding aircraft leased out or sold by players:
IMO, it adds liquidity, rather taking away from the liquidity. An aircraft that is ordered by an airline for its own use, that aircraft is locked away from me, pretty much forever. OTOH, if a player puts it on the market, even if the price is high, I have an option of buying it, leasing it, at whatever premium the seller / lessor choses.
I have taken advantage of it, more than once.