Ok, I didn't actually had all my facts straight about this in the #SaveMWO #ResurrectMWLL thread, so I'll explain what works and how, and where I was wrong:
First, a video of how its supposed to work: https://www.youtube.com/watch?v=3fePBRK69hU
(Unrestricted Free Reticle and Fixed Reticle, toggling between both with one key)
For an "Unrestricted Free Reticle" you need cl_free_reticle_independent = 0 and "toggle_free_reticle" On. For the "Fixed Reticle", cl_free_reticle_independent = 1 and "toggle_free_reticle" Off (which is by default).
To achieve a toggling key between both methods, this is needed in your actionmaps.xml and your active_actionmaps, inside the <actionmap name="mech" section:
<action name="toggleIntCvar cl_free_reticle_independent" onPress="1" consoleCmd="1">
<action name="toggle_free_reticle" onPress="1">
<action name="center_free_reticle" onPress="1">
And your autoexec.cfg needs to have con_restricted 0
and cl_free_reticle_independent 1
So now when you start a match you will have Fixed Reticle (as cl_free_reticle_independent will be 1 and toggle_free_reticle will be Off). When you press the key you chose (in my case its left alt) it'll now switch to cl_free_reticle_independent 0 and toggle_free_reticle On, giving you "Unrestricted Free Reticle".
And that's it. I was wrong before when I said "toggleIntCvar cl_free_reticle_independent" wouldn't be needed, because we still need to switch that CVAR.