I think this idea will work better for a land unit becasue there's already a shield generator on land. I want to produce one using the SPMAT or the ATAA model but I dont know how to limit the shield activation to only when an ability is used (eg. deploy or a shield abilty)
The so called shield on the capital ships are only a behavior + an extra bar of health that regenerates + a visual effect when something hit it. One way I think think of is giving the 'shield ship' an area effect abilty like the 'missile shield' of the interdictor but you substitute your ability instead of the missile shield.
Your shield abilty should force the surrounding friendly unit in the area to redirect damage to this 'shield ship' (of course you must give this shield ship more shield points or regen rate when the abiilty is activated). There's unit that do this. Only the tie_prototype and Luke_xwing that do the other way round by <Redirect_Damage_To_Teammates> (it's limited to the squad only). This is the only idea I can think of but it's rather impossible.