I tried to test with Electrum wallet and there is no way to do that with a hot wallet.
My post was hypothetical: "it would be nice to make this a hidden feature". It doesn't exist (yet).
In principle this is an interesting idea, but I think you would have to be very strict and knowledgeable to game the chain analysis companies with this strategy, to prevent them to apply clustering techniques. If this became a widespread privacy technique, they could for example only take into account connections where an outgoing (broadcasted) transaction was received from the client.
That would be a
huge win for privacy, as it means they can't assume any addresses synced by a wallet belong together anymore. Add the fact that Electrum frequently connects to a different server, and thus they won't see the majority of all broadcasted transactions, so they can't possibly know what belongs together anymore. But again, this is pure hypothetical. Loading random watch-only addresses would also add an increased load on the Electrum server.
In older Electrum versions you could import private keys also into "normal" wallets, but this feature was removed afaik.
I get why they did it, but for someone who considers himself to be an advanced user, I would like to get back that feature.
A problem is of course also the practical aspect: you would have to set up an "alternative" strategy to use your wallet normally, at least if you transact and not HODL only.
That's easy: on your watch-only wallet with imported addresses to mix with your own addresses, freeze the ones that aren't yours.