### 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_
{"includeWatching", UniValueType(UniValue::VBOOL)},
                {"include_watching", UniValueType(UniValue::VBOOL)},
                {"inputs", UniValueType(UniValue::VARR)},
                {"lockUnspents", UniValueType(UniValue::VBOOL)},
                {"lock_unspents", UniValueType(UniValue::VBOOL)},
                {"locktime", UniValueType(UniValue::VNUM)},
                {"fee_rate", UniValueType()}, 
                {"feeRate", UniValueType()}, 
                {"psbt", UniValueType(UniValue::VBOOL)},
                {"solving_data", UniValueType(UniValue::VOBJ)},
                {"subtractFeeFromOutputs", UniValueType(UniValue::VARR)},
                {"subtract_fee_from_outputs", UniValueType(UniValue::VARR)},
                {"replaceable", UniValueType(UniValue::VBOOL)},
                {"conf_target", UniValueType(UniValue::VNUM)},
                {"estimate_mode", UniValueType(UniValue::VSTR)},
                {"minconf", UniValueType(UniValue::VNUM)},
                {"maxconf", UniValueType(UniValue::VNUM)},
                {"input_weights", UniValueType(UniValue::VARR)},
            },
            true, true);
        if (options.exists("add_inputs")) {
            coinControl.m_allow_other_inputs = options["add_inputs"].get_bool();
        }
        if (options.exists("changeAddress") || options.exists("change_address")) {
            const std::string change_address_str = (options.exists("change_address") ? options["change_address"] : options["changeAddress"]).get_str();
            CTxDestination dest = DecodeDestination(change_address_str);
            if (!IsValidDestination(dest)) {
                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Change address must be a valid bitcoin address");
            }
            coinControl.destChange = dest;