I'm working on a bitcoin application which talks to Bitcoin Core. It uses RPC commands to request information about which bitcoin addresses from a HD seed have UTXOs are on them. I'm thinking about making this wallet synchronization work with a pruned node.

Given a HD seed, one way to synchronize the wallet would be to import a lot of watch-only addresses into Bitcoin Core and then restart it with -rescan. This would require the pruned node to redownload the entire blockchain again [possibly multiple times(!) if I didn't import enough watch-only addresses] and then use listunspent RPC.

So I'm thinking to query the UTXO set. I wouldn't get transaction history information but that's okay for these uses. I'd need a way to go from address to UXTOs.
1) One way would be to simply use the RPC calls getbestblockhash, getblock and gettxout to step through all outputs in the entire blockchain, checking if our addresses match any of them.
2) A second way would be to write some new RPC calls that allow dumping of the UXTO set database with pagination in the manner of listtransaction, then check if our addresses match.
3) A third way would be to open the UTXO BerkeleyDB database file (can this be done while Bitcoin Core is running?) and then check if our addresses match.

Another issue is that currently pruning disables the Bitcoin Core wallet so -walletnotify probably wont work. This doesn't have to be a problem as I could just poll getrawmempool and use -blocknotify instead.

Thoughts? What's the best way to proceed?