Well, I ran this issue to ground, and at the end of the day, while the links plugin strategy works like a charm, the web tools plugins that can work with PDT 0.7 cannot work with RSA due to a early conflict with a number of RSA's plugins, including JSF.
I submitted this situation as an eclipse bug, but (and who could blame them) the web tools maintainers pointed out that compatibility with IBM's V3.2 plug-in's was hardly their problem, and the PDT maintainers pointed out that a 0.7 release (needed because all the IBM tools target a 3.2 eclipse) is hardly theirs.
And their position has justice. I'd have said the same.
Bottom line ... IBM includes plugins that are guaranteed to work together ... in order to assure support, but are not terribly compatible with many other more recent plugins. If you want to use RSA you can expect version lock as the price you pay for the enhanced capabilities (mostly graphical editors and UML tools) and support.
Damn. Those are very good UML tools and graphical editors.
What does seem to help, though, is pointing both a new 3.3 Europa eclipse and RSA at the same workspace. You get workplace setting conflicts, but that's not a matter for great concern; just reopen your views. You can't do both at the same time, and pay the price of a slow switch, but the situation is workable.