Add to the mech lab, don't ruin it. Create buildable modules that can be tinkered with in the mech lab. You could get the module parts by purchase, supply crates, or drops should want to add that to say faction warfare if you wanted to push it. Modules once placed would have to be destroyed in order to open a slot giving the credit sink you're looking for. Tiers of modules could be used so newer or poorer players are using subpar modules until they can afford or have put the time in to build better. I want to see you make money so you can invest in whatever% back into the game. So add in this module thing so you can create more micro transactions.
Sell pilot bays instead of mech bays, as you'll need less pilots in this way you can engineer it to meet your bottom line by selling them for whatever your accounting works out to say 3000 mc. One pilot=10 double mechs. Double mechs would still be created anyway because of people not wanting to break there modules.
I realize this skill tree is someone's baby, so I came up with these ideas with that in mind, as to make good use of it.
Edited by JumpenJack, 08 March 2017 - 06:12 PM.