An auction with which many of us are familiar:
2♠ here, of course, is a power raise of Opener's minor.
How about this permutation?
I mean, can 2NT to play be right? How much better to get under 3♣/3♦ to make a game try if your "practical pass" has just grown up? Partner might simply be competing, but he might have a very powerful hand. Game is still in play, but forcing the four-level to explore this possibility seems a bit rich, even if it happens to be justified. Why play 4♣/4♦ just because it really should make when a strange stack or surprise somewhere might limit the hand to 9 tricks?
If Opener hears 2NT, he can sign off with a hand that would decline an invite. With interest in this new enthusiasm, Opener can always do something intelligent to see what your basis for enthusiasm may be. A reasonable approach to this would be to bid the other minor as an asking bid, allowing Responder to cue a feature (including a 3♠ bid as "shortness"). Or, Opener could bid 3♥ to show that his short suit is void, 3♠ to show a suit playable opposite a doubleton (or maybe even opposite a stiff honor?), and 3NT to show a primed-out hand.
I really like Opener's rebid of spades at this point to indicate playable opposite a stiff honor. Imagine, for example, these hands:
Opener: ♠AKJxx ♥AJx ♦x ♣Axxx
Responder: ♠Q ♥Kx ♦xxxxx ♣Kxxxx
3♠(playable opposite stiff honor)-P-4♠-all pass.