I'd posted this idea on the Facebook group and there was some good discussion about it. You can see that here, if you're interested:
Here's where I got to at the end of all that. The "No hull total" column is the plane's max speed + top manoeuvre + throttle - handling. It's "no hull" because at one point I was thinking of subtracting hull, but decided against. It didn't change the order much and resulted in negative numbers, which was odd. People felt that this gave us too big a range of numbers, so I halved those values in the next column (rounding up). I then gave all planes with only 2 hull a +1 bonus, to represent the advantage of having a light weight fighter*.
So the idea is that, in the movement phase, planes should activate in the order of their score in the right hand column. Grot Bommers and Marauder Destroyers would be first with lightnings and barracudas with afterburners last. Ties would alternate as in the standard rules, so if barracudas and lightnings fought, whoever was going first would move the first one.
Lockdown has meant I haven't yet tested this system. I think it removes the advantage of having more planes, which is good. It also means that, in general, the tougher, shootier planes will have to move before the flimsy, lightly armed ones. I might actually take a lightning instead of a thunderbolt in this system, for example.
However it might be a problem that it's a bit fixed. A dakkajet always moves after a thunderbolt, for exmaple. So there's an option to add some randomness. At the start of each turn you'd roll a D6 for each plane and add that to its initiative score. You'd need to keep track of that with something like a D20 by each plane. I think I prefer this as it means a pilot might sometimes have a moment of inspiration to do better than expected (or less well!). But it adds to the complexity, which is not ideal.
*AKA the "but why would you take an avenger?" bonus.