Said it before but I'm all for the idea of removing restricted slots, but....
Doing so would require a serious "balancing pass" to ensure it had no unintended consequences.
The game is in need of a serious balance pass regardless, because the slots themselves had unintended negative consequences.
Military slots are primarily for HRPs. Even though they can be used for banks and MRPs, those items are usually best placed in other slots because most military slots are either insufficient in size or don't allow for intelligent module protection stacking. It's generally a space for hull boosting that gives ships a major combat advantage. The original reason these slots were given to us was so that combat ships could retain their hull boost and then have room for cargo, because most missions and engineering mods back then required ships to have free cargo space. It also provided room for the new MRP module that was needed after realizing the unintended consequences of weapon and hull power creep. Hull tanks had become completely worthless.
It was a choice that solved the problem certain ships were facing, but created new and unanticipated problems of which I think Frontier only recently acknowledged: Health Disparity between PvE players and engineered PvP players. The difference is quite staggering, where one can usually soak up 10 times more firepower than the other. This doesn't do well to create an inviting environment for newer players. They feel incentivized to hide in solo, download hacks, whine about griefers, and combat log. That's a shame.
Their alternative choices could have been:
a) Give all ships a permanent base amount of cargo space without requiring a module for it.
b) Increase core hull values while decreasing Hull and HRP engineering mods.
c) Not provide cargo for rewards and remove cargo requirements for engineering mods (Was Done Later)
d) Adjust core module health values, perhaps further enhanced integrity benefits for B grade modules.
e) Revert power creep and hull tank nullifying special effects.
f) Enhance base shielding while reducing shield mods by a lesser extent.
g) Completely changing the function of shield boosters to be module shields (MRPS), then removing MRPs and enhancing base shields further to compensate.
What negative unintended consequences could be produced from any of these alternative solutions? I really can't think of any, but I can think of a lot of positive benefits.