i meant that in his system you could smite twice(or more) even if you don't have extra attack
I mean, if Larian implemented it this way, sure. But since Smite is part of an attack (with an action cost) and isn't actually a reaction, theoretically they wouldn't.
And even if they did, you'd still be limited by the # of spell slots. I suppose the most likely way Larian would implement is: you'd be able to stack smite multiple times on the same attack, but it wouldn't allow *extra* attacks. Is that what you meant?