I almost agree with you. Only thing I am warrying about is compatibility. But it seems to depend on JBoss versioning policy, so if you say no problem, then it's OK :)
We accept breaking compatibility at a major release. We don't want to go crazy introducing incompatible stuff, because that does make upgrading harder. But, on the other hand, it's good to be able to use a major release to clean out old ways of doing things.
With snaphsot mode, it's borderline. The benefit of removing it from the Tomcat SAR config is not that great; mostly it just removes from the xml a bunch of complicated explanation of a feature people don't use. It also reduces coupling between the depployer and the webapp (less data needs to get passed into the webapp.) But some data (useJK) still needs to get passed, so the decoupling benefit isn't that great.
I'm inclined to remove it from the sar mostly because I don't think it's used. For example, I've never seen a forum post related to the behavior of "interval" snapshot mode.