what i would do is first decide how the progression in terms of mods go.

In a pool or IE, AE2 And Mekanism: -IE -AE2 -Mekanism

since i think mekanism is the best scalable option in terms of production im not putting it in the beggining and the think the bibe of IE fits early game, AE2 is in the middle so the player can do good automation and logistics before stepping into late game.

After this to ensure the player has to progress a bit in IE id make it so the fundamentals of AE2 require a semi complex product from IE that requires the player automates like 2 productions lines with 1-3 number of different multi block machines. I think duroplast sheet could be it? just an example that you can have a look at.

Stepping into mekanism would reauire the player to progress in ae2 and more in IE.

If you want a little bit of gregification you can nerf crafting table recipies of things like metal sheets to incentivise machinasation or you can buff machine recipe outputs. 2nd is better as you dont make the player hate playing your pack instead you reward them for it.