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You cannot change the address format of an Omnilayer address. A valid OmniLayer address has to be a Bitcoin address; the transactions are being done on the Bitcoin Blockchain itself. If the address isn't a Bitcoin address, then the transaction wouldn't work.
it makes no sense to do something like this because you are still sending bitcoin on bitcoin blockchain to a bitcoin address but it is not impossible to implement considering the fact that we have 2 separate "wallets", a bitcoin wallet and an omni wallet.
so theoretically tether could introduce a different wallet encoding (or simply a different version byte) so that its addresses are rejected by the "bitcoin wallet" and the bitcoin addresses are rejected by the "omni wallet" while they both decode to the same scriptpub.