Configuring Fields in Application Composer

Summary:

We are looking at the possibility to change the LOV associated with a Fixed Choice List Field that is already published with a Sandbox and are looking for ways to see if it is possible to achieve one of the following options:

1. Best - If there's a way we can be granted more fields in the instance maybe through SR?
2. Better - delete the fields so we can have more multi-select picklist (we have a lot that we need to create and some are more important than others after the fact that the limit has been met) maybe through SR?