Custom pool option should offer input field for Bitcoin reward address as default

[314159265359879]

Given that a users select the "custom pool" option when stacking in a non-custodial pool.
They should be presented with input field to add bitcoin reward address.
The user is not, and left puzzled where the pool operator should send the bitcoin rewards.

This guide was followed by the user:
https://docs.blockdaemon.com/docs/how-to-stacks

See issue:

When a user selects Planbetter, or Xverse (pools also known to do payouts in Bitcoin) the input field for a bitcoin address is presented as expected.

[friedger]

How does block daemon determine the reward addresses of pool members?
a) expect the user to enter a btc address though the pool contract? Requires a allow-contract-caller call.
b) determine a btc address (which derivation path) from the stx address?

How do we expect unknown pools to handle the reward addresses?

Is this issue about using a) as a default?
Or should we add a second option "Custom Pool with btc address"