The idea for a 'heavy' fast mover always intrigued me, given my stun throwing and knife spamming playstyle in COD back in the day which I hope to bring to EC in the form of a Raptor class.
Here I was inspired by the idea of a 'balanced/non-imba' "Heavy Raptor" character that operates on a literal "fight-or-flight" mechanic, with little room to change or combine tactics once engaged in full-on combat, and favours positioning and reflex oriented playstyle.
The core mechanics:
1) Replace the standard armour value with a quick recharging shield.
2) The shield value also shares the same energy as the flightpack.
3) Mobility on foot is increased due to reduction in armour mass.
So by design, Nostos is essentially a "lightweight" armourless Raptor in nature, but given the electro-reactive armour /ERA mechanic, uses flightpack energy to create a rehargeable shield that replaces conventional armour, theoretically making him "heavy" by compounded armour values over time. On the "lightweight" hand, he is much faster to kill under accurate, sustained fire than your standard raptor. On the "heavy" hand, allow him to escape, and he comes back fresh as before you opened fire.
If he is hit, the suit energy drain dramatically reduces his ability to utilise his flightpack or psycho-warfare systems. Once he absorbs enough oncoming fire, his flight pack is 'grounded' and while waiting for it to recharge, has to fight tooth and nail to regain a tactical advantage. If he takes off, with whatever juice he has, accurate fire will drop him from the sky as well.
The ideal playstyle is to be nimble, mindful of positioning, picking fights and taking calculated risks in full-on assaults, being aware to manage electro armour/flightpack drain. The safest (cowardly) play is a combination of loitering while avoiding AA fire, picking out targets, then diving in for high speed DFAs, and taking off, factoring a few hits here and there.
The most fun play, I imagine, is dropping straight in and letting the energy go into absorbing damage, exploiting foot mobility and short bursts, vectoring around hostiles and going for melee takedowns, like the Night Raptors of lore
Fluff wise, I thought having his superconducting bolters creates a random 'microstun' effect on targets that are hit would be quite fun and annoying too, allowing him to play a loiter-support role if need be.
I think it should be represented with standard armour value reduced to 4+ (this is carapace armour level protection) but has an invulnerable save that degrades for each wounding hit for that turn. The first hit will result in the highest invulnerable save but each hit will degrade the save for each single hit after the first. If the starting invulnerable save starts at 3+, then the second save degrades to a 4+, the third save becomes a 5+ and the 4th save would become a 6. The 5 the save would deplete the electro charge meaning you have to use the armour value