The current problem is that the code provided interfered with the multiplayer code, and needs to be adjusted to address that issue.
The feature wasn't rejected, it was put in triage because it is not as simple as it sounds and the volunteer who wrote a patch hasn't written an acceptable patch.
If you want to build a version with this feature, and forgo multiplayer, you can. The code IS available on github.
As of people wanting to fix this patch.
It needs the following:
1. It needs to apply multiplayer code from the brakes to the block brakes in order to fix any syncing issues.
2. Debugging is needed to insure it isn't exposing any previously unknown desync bugs in the braking code.
3. Because the code executes on a block brake (a severely desync prone part), strong desync protection may need to be added.
While others may debate this position, my caution against desync bugs over performance states that strong desync protection should be added to all brakes considering it is a key point in a roller coaster that can cause minor desync bugs. They are often put in roller coasters to make sure the roller coasters behave the same between runs. They are literally desync protection for roller coasters. Having your desync protection desync is bad on every level.