If they're able to base Mega-Weavile off some Sonic the Hedgehog character such as Super Silver, I don't believe it would be to bad; many of us would rather enjoy it, I'd imagine. If they would like things to be more precise, I feel Shadow would be a good option, too, especially they sort of share the same color-scheme (only difference is that Shadow's a little more dark).
Mega-Aerodactyl isn't so bad, but to me, it seems that they haven't put much thought into its stats and ability, sadly. Aerodactyl is overly-speedy, which is great, but its defenses don't allow it to endure much hits (same goes for its mega-form), causing it to get taken down as soon as it changes form. It would've been nice if they had allowed it to gain defensive boosts and endure few more attacks.