I would probably be supportive of preventing address reuse on the protocol level. Currently it's such a hard sell to tell people to not re-use addresses. I sell bitcoins and most of my trading partners re-use addresses. But I'm also a bit guilty as I'm sometimes using Phoenix where technically I might not re-use an address but it's trivial to track what's spending and what's change for those and many other transactions. Also please stop your affinity for round $$ amounts. The 200$ UTXO is always the payment when the other amount is something odd in $$. Etc. etc.