Some comments from @sipa in #12702.

___

Yes, I think `importmulti` is superior in every way, except:
* Slightly less convenient to use (it requires redundant information, as you have to explicitly state what you want to import, and then give the keys/... to enable that).
* ~Doesn't support P2SH-P2WPKH yet~. Added in #14454

The latter can be fixed by just adding support for that case. The former can be improved by adding 'default' cases (e.g. if you prove a WIF private key, it can permit omitting the address, ...).

pwallet->GetScriptForMining(coinbase_script);
    
    if (!coinbase_script) {
        throw JSONRPCError(RPC_WALLET_KEYPOOL_RAN_OUT, "Error: Keypool ran out, please call keypoolrefill first");
    }
    
    if (coinbase_script->reserveScript.empty()) {
        throw JSONRPCError(RPC_INTERNAL_ERROR, "No coinbase script available");
    }
    return generateBlocks(coinbase_script, num_generate, max_tries, true);
}
UniValue rescanblockchain(const JSONRPCRequest& request)
{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
    CWallet* const pwallet = wallet.get();
    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    if (request.fHelp || request.params.size() > 2) {
        throw std::runtime_error(
            "rescanblockchain (\"start_height\") (\"stop_height\")\n"
            "\nRescan the local blockchain for wallet related transactions.\n"
            "\nArguments:\n"
            "1. \"start_height\"    (numeric, optional) block height where the rescan should start\n"
            "2. \"stop_height\"     (numeric, optional) the last block height that should be scanned\n"
            "\nResult:\n"
            "{\n"
            "  \"start_height\"     (numeric) The block height where the rescan has started. If omitted, rescan started from the genesis block.\n"
            "  \"stop_height\"      (numeric) The height of the last rescanned block. If omitted, rescan stopped at the chain tip.\n"
            "}\n"