If you have an idea to improve Sushi that needs to be approved by the community creating a proposal on the forum is the best place to get feedback and share it with the sushi holders.
It's very easy to create a proposal:
Step 1: Go on https://forum.sushi.com and create an account.
Step 2: Then back to the home page and click on "new topic".
Step 4: To get more traction, don't hesitate to share it on discord and twitter.
If your proposal has enough traction it might be posted on snapshot by the core team, if the vote is succesful it will then be implemented.