I usually answer this kind of mails, but I will hold my answer to wait some feedback from the rest of the community and the project leader.
These are all interesting features that everyone could benefit from. So if you are actually doing improvements like this, I would suggest that if you could make them configurable somehow, you could donate these back so they even become part of the project so you don't have to maintain your own version.
To get started, simply forking the jbpm codebase and doing modifications there is probably the easiest. And we welcome any pull requests for features you think might be useful for the entire community