I'd start a parallel process where you check in with the team in specific ways relevant to the boredom-type issues you perceive. This could prevent you from causing the spread of one problem into two problems:
1) The need to refactor & unit test
2) The perceived need to take part in $team_motivator's challenge idea thing
I'd ask team members:
- How does this project feel to you lately (do they use words like boring / ineffective?)
- What can be done to make this easier on you?
- Anything else you want to do that's not this thing? (Like an unrelated project)
This should be a recurring meeting, where you check in over time.
This way you can remove your own ego-hero from the process, which is known to interfere and boost you while preventing the boosting of others' ego-heroes, thus handing control and interest back to them where possible.
Then what you can do is start to collect ideas, start an idea board, and feel for responses to your idea.
If your idea gets some traction, then you have authentic buy-in to your authentic idea and ergo--team permission & encouragement.
Good luck