What if it's implemented in a different way, when placing your BTC address in your profile you're required to sign a message using it, if the message is valid the balance will be considered as 'available'. It won't remove scammers, but will make it harder for them to use random addresses claiming its theirs, and will be easier for normal users to view valid funds instead of going through the process of manually confirming it with dealers.
Good suggestion (as long as the whole process is automated and not mandatory) but not sure same can be done for other "cryptos" (based on OP's concern). For verified addresses, a "green check mark" can be added next to them and for unverified addresses, a red "X".
On a side note: This thread belongs to "Meta".