I suggest raising the maximum company AE's level to 10, no matter how expensive it gets, I think it's worth it.
If it is going to happen, my expectation is that it would cost 1280 steel for the level 8, and 2560 steel for the level 9, and 5120 steel for the level 10.
That would make steel prices insanely expensive, I would like to rise the maximum allowed number of companies for the same player to 15, that would balance the concrete a little bit compared to the steel.
This will make a company AE level 10 in 1 day with a bonus of 62% can produce 388.8 production points, rather than the 272.16 of production points of AE of level 7 produced in 1 day, this means the development is 116.64 in one day more than the AE level 7, this means, that it will pay its cost of steel to reach level 10 after 1536 days, and after that only the profit will start, even though, I think it still worth it, for me as a player that don't think I will quit the game anytime soon.
The players who maxed their companies should save steel for such an update like that from now, also because steel prices will be much higher.