While I see where you're coming from, we're certainly not seeing a huge amount of bankruptcies, plenty of airlines are thriving, so I think it's a rather unfounded basis really.
You only need a large amount of aircraft to cover the fixed costs once you start getting into the 4th and 5th or more fleet types. The first 2 or 3 have very minimal penalties for operating additional models and minimal upfront overhead -- the total commonality costs to put the first F28 into my fleet for example was a mere $25K/week. You're easily able to have consistent growth even while operating just a single model of a 2nd or 3rd model, it's the later new models that can kill ya.
It's all part of a strategy of slowing growth as well as making things more realistic and frankly I find it much more interesting and fun than the old way. And rather than causing so many bankruptcies, this is drawing out the truly competitive phase of the game (as opposed to later where everyone's got so much money it's not really "competition" anymore), creating much more diversity at major airports than there usually is at this point in the game where it's getting down to 1, perhaps 2 prolific carriers at each, as one has usually already dominated the market and worked on wiping out the competition.
The pace of deliveries along with lack of multiple legs has kept a much more even pace of development amongst competitors, forces a much more realistic longer-term outlook (rather than world domination in 12 months), and made the early decisions of competition vs open route much more important than in game's past, and is all in all shaping up to make a more interesting game than we've seen before.
If I were to make any suggestion at all, it'd be to continue this trend of slowing growth by targeting the play strategy of the top few percentage of players that are able to secure extremely large sums of money early on and game the system into even larger loans thereby securing exorbitantly large aircraft orders. We've already hit the strategy of "fly-anything-you-can" with the exponential penalties on fleet types (but it needs even more work), now we just need more work on going after long-haul revenue and costs similar to how the domestic game got a LOT more interesting with the red-eye demand penalties.