### 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_
throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both estimate_mode and feeRate");
            }
            coinControl.m_feerate = CFeeRate(AmountFromValue(options["feeRate"]));
            coinControl.fOverrideFeeRate = true;
        }
        if (options.exists("subtractFeeFromOutputs") || options.exists("subtract_fee_from_outputs") )
            subtractFeeFromOutputs = (options.exists("subtract_fee_from_outputs") ? options["subtract_fee_from_outputs"] : options["subtractFeeFromOutputs"]).get_array();
        if (options.exists("replaceable")) {
            coinControl.m_signal_bip125_rbf = options["replaceable"].get_bool();
        }
        if (options.exists("minconf")) {
            coinControl.m_min_depth = options["minconf"].getInt<int>();
            if (coinControl.m_min_depth < 0) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, "Negative minconf");
            }
        }
        if (options.exists("maxconf")) {
            coinControl.m_max_depth = options["maxconf"].getInt<int>();
            if (coinControl.m_max_depth < coinControl.m_min_depth) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("maxconf can't be lower than minconf: %d < %d", coinControl.m_max_depth, coinControl.m_min_depth));
            }
        }
        SetFeeEstimateMode(wallet, coinControl, options["conf_target"], options["estimate_mode"], options["fee_rate"], override_min_fee);
      }
    } else {
        
        coinControl.fAllowWatchOnly = ParseIncludeWatchonly(NullUniValue, wallet);
    }
    if (options.exists("solving_data")) {
        const UniValue solving_data = options["solving_data"].get_obj();