### 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_
#ifndef BITCOIN_WALLET_FEEBUMPER_H
#define BITCOIN_WALLET_FEEBUMPER_H
#include <consensus/consensus.h>
#include <script/interpreter.h>
#include <primitives/transaction.h>
class uint256;
enum class FeeEstimateMode;
struct bilingual_str;
namespace wallet {
class CCoinControl;
class CWallet;
class CWalletTx;
namespace feebumper {
enum class Result
{
    OK,
    INVALID_ADDRESS_OR_KEY,
    INVALID_REQUEST,
    INVALID_PARAMETER,
    WALLET_ERROR,
    MISC_ERROR,
};
bool TransactionCanBeBumped(const CWallet& wallet, const uint256& txid);
/** Create bumpfee transaction based on feerate estimates.
 *
 * @param[in] wallet The wallet to use for this bumping
 * @param[in] txid The txid of the transaction to bump
 * @param[in] coin_control A CCoinControl object which provides feerates and other information used for coin selection
 * @param[out] errors Errors