Somewhat Cheesy Knowstone question

[Matthew Morris]

Can another spontanious caster (Beguiler, Bard, Warmage etc.) take advantage of a knowstone via Use Magic Device to use their spell slots to cast a spell not on their list?

Here's my logic.

Warmage has a knowstone of detect magic. Detect magic is not on their list (How does a warmage detect magic? Anything that survives the fireball must be magical) He uses 'Emulate class feature' from UMD to emulate the spell being on his class list.

Is 'Having the spell on your class list' a class feature? Or is 'Ability to use a knowstone' a Sorcerer class feature?

I don't see it being horribly broken to go this route, but would like other opinions.

[Zherog]

I think it's quite reasonable to allow UMD to "emulate a class feature" that would enable a knowstone to work.