runeglaive is like a closer cousin to ludens you have to think of it in this manner.
if lichbane was spell effect it could spellvamp which you absolutely cannot have unless you did something to it....
ahem: see this solution.
here's how a dynamic lichbane would look like:
http://i.imgur.com/ie1gASUh.jpg
it could spellvamp off of equation 1 but not 2 even though it could still do equation 2 worth of damage.
as an on hit effect and one that scales with deathcap (ap's equivalent to IE), it'd be as though you could spell vamp off crits. there's a reason lifesteal is less than spellvamp since spells are gated by cooldown of spells.
Crits while not classified as such, are a close cousin to on hit effects. If anything lich bane's on hit effect resembles crits closer than they do regular spells.
ludens has charges too which gates its ability to spellvamp.
Say we were to implement this suggested improvement to spellvamp i posted here: http://boards.na.leagueoflegends.com/en/c/gameplay-balance/TaXPYTao-spellvamp-100-scale-on-aoe-but-with-100-cap-as-thoughwas-singletargetoverlap-w-current-equation
runeglaive would likely op since it would sustain at 100% value as well. so you'd have to apply this dynamic feature to it as well.
its doable for sure but riot needs to approve/be behind it.
or perhaps items could just behave in their own unique way and just sustain off 33% if aoe.
