Currently using BC Vault with MetaMask is not possible. MetaMask is responsible to add support for any new hardware wallets and thus the decision is solely on their side, we would be more than happy to add support for BC Vault, when they decide to include it.
BUT there is absolutely no problem to use BC Vault with your favourite DeFi/NFT site, since BC Vault from v1.7 support WalletConnect.
WalletConnect is practically identical functionality supported by all major DeFi/NFT sites.
Please see: WalletConnect - DeFi dApps