What if you have a low fee transaction and want to raise its fee so it is mined, but are unable to resign it?
An example is an old cosigned unpublished transaction made when fees were lower.

Solution:
You send a miner money off-chain, for them to include your transaction in the block.

Any protocols that rely on cosigning without publishing face this problem of not knowing the fees in the future.

This may be helpful with the lightning network, where fee price fluctuations make it so commitment transaction fees are really high. Right now I believe commitment transactions are set with a high fee to avoid fee volatility.

Unsure if anyone has thoughts on this service would help the lightning network or other products.
Or if this idea has been thrown around before.