It is generally discouraged to receive more than one payment to the same address. One reason is anonymity (not only the receiver's, also the payer's anonymity), the other reason is that if you have two outputs to the same address, you're unlikely to spend them both at the same time, so the public key will be revealed before you get to spend the second output. I am saying that this general guideline is not compatible with using intermediate tree nodes for receiving, because an intermediate node is too "static" (it roots a subtree which probably has a significant lifetime). Only leafs are suitable "one-time objects".
I don't really see the problem here. The default HD wallet layout that probably most users will have is just one or more subaccounts where the subaccount is an unbounded linear path, meaning that it'd be similar to the current random-independent wallet in the sense that the user would just keep generating new receiving addresses as needed, except that your initial backup of the root node is enough to restore all the subsequent privkeys, and greater security / less hassle because there's no need to access the encrypted privkeys in order to generate new receiving addresses (plus the other possible benefits like type-2 pubkey delegation and brainwallet passphrase).