Peter Bregman has a great post on How to Counter Resistance to Change.
He makes several great points, and I recommend you read the full article.
Here are two gems:
1. “People don’t resist change, they resist being changed.” That means they can often go along with change if they have some level of control and decision making in the process.
2. “Don’t sell it or try to get “buy-in.” Instead of seeking agreement, try to surface disagreement.” This is both how you allow for that control mentioned above and how you improve your proposal by incorporating feedback.