Based on your description, the slot connection is probably the way to go (in WF2). Since you can create a datum curve to reference the stops, you can change the size of the cylinder body and the curve should follow suit, thus changing the slot, and therefore the translation limits.
It would be great to see parameters like this made available in other modeling modes of Pro/E. Having things like Joint Axis limits and regeneration values available for Family Tables and such would be a HUGE step.
The little time I've had with WF3 has shown some steps in the right direction, but needless to say, I'm cautiously optimistic...