I think the perks could do with a rework. Each level, you only get a choice between two options, and half the time it's not a real choice because it's a choice between melee or ranged, so you just follow whichever one you're already specialising in.Personally I'd like the classes removed and perks gained from level through a differernt mean than, you are merc so you get cluster grenades or C4 bomb. Id like something like COC where you could get any perk as long as your char was strong enough or fast enough for them. Or another class like Rusher where you get acess to all the class perks when you level up but can only pick one from that lvl.
The system you describe could work, but it'd need a loooot of balancing. The system you described has a little bit of weirdness where a character can minmax and take ten perks which are completely unrelated in order to create a jack-of-all-trades super soldier aka merc
All the classes have perk tiers which are pretty mediocre, but they come at different levels, so by picking perks from different classes you can avoid the crappy ones. For example, Smuggler gets to pick between the super situational Quickdraw or Leap Up perks at level 6, but if you off-class, suddenly you have access to the consistently powerful +20% damage perks that Tech and Merc get.