Feature:
The only current use for the withered bonemeal is as stepping stone for the withered bone blocks. So how about make it possible that you can withered bonemeal a wither rose?
Note: Use the New block template for blocks specifically! This is for non-block requests, such as compatibility suggestions.
Describe what the new feature should be. Generally, the more information you provide, the faster we can decide on whether it is something we can/will do. Make sure to check our roadmaps first before making a suggestion; we may already have plans for what you're thinking!

Alternatives:
It won't fit to have it bonemeal any other plants except if you want to kill them and leave nothing/a wither rose behind?
If this feature has possible alternatives, such as different implementation methods, list them here.

Additional info:

Any other info should go here. With more complicated features, it is geneally worth mentioning even the smallest of details you wish to see if the suggestion is approved and implemented.

The original idea was to have withered bone meal kill crops or plants it is used on, although that didn't end up being added and its unlikely that it will any time soon. Having some interaction regarding wither roses isn't a bad idea though