In terms of fluff and picturing an epic combat the concept is very nice, but the added value to the game is sorely limited (because of animate weapon).
The unupgraded is something of an addition, because it doesn't require
; the upped one adds something only in a 'mono only' restriction setting.
All in all, it's UP, because shields are quite important. You could make the unupped cost 1 :other and the upped one free.
Another thing: is it reversible?