### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current behaviour

See inline discussion at https://github.com/bitcoin/bitcoin/pull/26467#discussion_r1269177446

@whitslack:

> Consider the case where I am paying someone on chain under the stipulation that _they_ will eat the mining fee. (Thus, I specify _their_ address in `subtractfeefrom` when I'm constructing my transaction.) Later, they tell me that they can't wait for confirmation any longer and need an urgent fee bump. If I naïvely specify their output as the `reduce_output`, I may end up paying them _**much more**_ than I intended to if I only have large UTxOs in my wallet.


### Expected behaviour

Not sure.

Improving the docs is one option, but this behaviour seem quite counter intuitive.

My own suggestion:

> Should we disable the adding of new inputs when `reduce_output` is set? If someone really intends to do that, they should probably use `outputs`.

### Steps to reproduce

Haven't tried.

### Relevant log output

_No response_

### How did you obtain Bitcoin Core

Compiled from source

### What version of Bitcoin Core are you using?

Master after #26467

### Operating system and version

Any

### Machine specifications

_No response_
}
            CAmount output_amounts_claimed{0};
            for (const CTxOut& out : rawTx.vout) {
                output_amounts_claimed += out.nValue;
            }
            if (output_amounts_claimed > total_input_value) {
                throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Assigned more value to outputs than available funds.");
            }
            const CAmount remainder{effective_value - output_amounts_claimed};
            if (remainder < 0) {
                throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Insufficient funds for fees after creating specified outputs.");
            }
            const CAmount per_output_without_amount{remainder / (long)addresses_without_amount.size()};
            bool gave_remaining_to_first{false};
            for (CTxOut& out : rawTx.vout) {
                CTxDestination dest;
                ExtractDestination(out.scriptPubKey, dest);
                std::string addr{EncodeDestination(dest)};
                if (addresses_without_amount.count(addr) > 0) {
                    out.nValue = per_output_without_amount;
                    if (!gave_remaining_to_first) {
                        out.nValue += remainder % addresses_without_amount.size();
                        gave_remaining_to_first = true;
                    }
                    if (IsDust(out, pwallet->chain().relayDustFee())) {
                        /
                        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Dynamically assigned remainder results in dust output.");
                    }
                } else {
                    if (IsDust(out, pwallet->chain().relayDustFee())) {