sunfire cape to spellvamp
would be cool imo.
I assume dead man's plate
works with lifesteal
imo if sunfire could work with spellvamp gunblade would be more viable on ad with off ap scaling champs like say aatrox etc.
reduced to 33% effectiveness (cap at 100% so three targets only) since its aoe and only vs champions not creeps.
or on say tanky ap junglers like: 
could build 
for aatrox xin or warwick:
other champs:
....
this on skarner Shen or reksai, volibear
( 
/
) (could go either way depends on team comp flexible if need more magic dmg)
would pair well with this update to spellvamp: Spellvamp 100% scale on aoe but with 100% cap (as thoughwas singletarget)overlap w/ current equation
and this to Sunfire Cape & Cinderhulk:
Both get deathmark like feature, if a minion is at the brink of death with say 30 hp so long as a minion has 40 hp or less it will die if the aura hits it.
NEWPASSIVE Sunfire’s aura executes minions at or below 40hp