Stat progression (in xcom) is stupid.
It doesn't fit the lore at all.
Early soldiers who can't even carry a rifle and can't throw a grenade further than a 3-year old is stupid.
Late soldiers who can shoot a fly mid-air at 5 km is stupid.
Stat progression should be cosmetic at best (+20% max).
Vanilla did an acceptable job at that as your soldiers are expected to die after 2-3 missions in average early game, 5-10 missions mid game and 10-15 missions late game. "Survivors" should be
rare.
At least that's what I think the game designer anticipated (I might be completely wrong here though).
I hated stat progression (or actually the whole soldier evolution concept) in xcom2012 and I hate it in openxcom mods too.
In total conversions (non-xcom themed) it's acceptable.
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Now to your proposal... I don't get what is the difference between Human, Augment and Linker... is it
just stat caps??
Because if it is just stat caps, we don't need "upgrades" for that... didn't everyone interpret their stat progression this way already?... and converting them manually will bring a completely unnecessary boring tedious micromanagement component to the game.
... at least that is my opinion.
If anything, I vote for xcom:apocalypse approach... separate non-upgradable classes with different stat min/max ranges (e.g. human, hybrid, android, ...)
But limiting their stats' maxima would of course be a very poor and frustrating choice.
I guess I am the only person here wishing for that... simple, elegant, effective, realistic, challenging, fun.
Of course assuming you don't fight bunny rabbits early game and predator-alien-xmen-hybrids late game... but that's not xcom either.