add flags like in the :shell command
Agree, there should be only one.
OK, Joshua is probably right that RegEx is overkill. But, the elephant is already in the room and performance is not in question, so whatever type of implemenation is done is not important for the end user. The one that gives the most extensiblity and the least code should be hence prefered one, hence the RegEx in the first place. Not to mention that people expect RE everywhere now days.
Also, my experience with open source users is that people almost certainly find good uses for stuff you didn't think of, and somebody will eventually ask for full RE in travel. I know it happened before on Total Commander forum (which does have lots of users so this issue popped up fast) and author of the plugin solved the problem with 3 modes as described. That is a fact and Joshuas observations are theoreticall.
But as long as it works as described, I really think any solution will suffice.