You see, i know it's fun to think about ways to make VP cards more interesting, and now that Inheritance exist, ideas that make them behave like other cards feel more acceptable than ever before. Still, your card creates the problem of having Treasure/Action cards, a thing which even Adventures didn't introduce (or did, but without combining the types). The main problem i have with this is not the confusion, but for how little an effect you introduce it. For most cases, you could have the same effect by having your card say:
"At the start of your buy phase, discard any number of Victory cards. +
per card discarded."
And even though it means you can't use it on VP cards drawn after your last play of [Some Appropriate Name], i'd argue that's often not even very different from:
"Discard any number of Victory cards. +
per card discarded."
Which in turn makes it, well, a more narrow Vault.
Edit: Sorry, i somehow missed that GendoIkari wrote the same thing shorter. Well, take this as me chiming in, then.