Can we change how custom fields behave for certain item types?

We are experimenting with the ability to apply custom fields to Users and Items. We've successfully built the following model:

Custom field: Supporting Team

• Single-select for Users (represents the team they're on)
• Multi-select for Items (represents the team supporting the project or task, narrows down the user selection list for Assignee)

We'd like to keep Supporting Team multi-select for Projects (since we also have a single-select Driving Team field for the team leading it up) and make it single-select for Tasks for clarity of reporting and assignment. We're also pushing behavioral changes so that tasks get split up if more than one team is needed to complete them, but this UI change would help a lot.

What other approaches can be taken to solve this challenge?