Lots of good info here.
Couple small things:
The A&Ks are decent guns, but they'll require work out of the box to be 'reliable', and you can basically ignore the box mag it comes with for anything other than display. Good luck getting it to feed from STANAGs without mods. If you're thinking about buying one, factor in the costs of replacing the motor, compression system, and buying a 'nut sack' mag right off the hop or don't bother. Once you do that, a CA or G&P gets a lot closer to being a reasonable buy.
I don't look down my nose at A&Ks, but it makes a lot more financial sense to buy one second hand and fix someone else's sadness/ boredom at a cheap rate than to go new.
It sounds like you're pretty set on the NATO thing, but have you considered an AK?
RPKs are hands-down the best recommendation for a starter LMG, without question. They're functionally identical to any other AK inside and outside, V3s can be done up solid as fuck, and a 'cheap' AK variant from some companies buys a LOT more external durability than nearly any other platform these days.
I'm buying back my old 249 from a team mate and un-cursing it because I want to / have to, but if wishes were horses, I'd be dumping money into a tacticlol'd RPK.