Well, if we want to reboot this debate, then some ground rules need to be determined:
A) What levels of cannon for both sides do we accept?
B) How do the universes interact?
C) What, if any, information do they get on the "other universe" when they transition into it.
D) Do we hand-wave physics so both sides can act as they do in-situ, or do we assume that each side is relegated to following the other sides physics structure?
E) Super-Entities and Sub-Deities - yay/nay?
My reasons for the above:
A) Cannon in Star Trek is usually pretty straight forward - what we see on screen, period. There are, however, some really great books that dive into things not covered on screen without superseding or redacting what we do see. Do we wish to allow this?
Likewise, in Star Wars, cannon is usually the same, except with it's several tiers. The problem here, though, is that some of the books and such from expanded universe promote incredible claims of power that we don't see on screen, and sometimes vice-versa. How/where do we reconcile this?
For both, there are times where what we see on screen simply doesn't match with what we have seen other times on screen - we should establish some system of outliers for these so we can safely explain why we have seen said events without attempting to pigeon hole either side into a specific set of strengths and/or weaknesses (example; should we assume Neutronium in Star Trek and Star Wars are the same thing, despite the fact that in ST Neutronium can only exist in neutron stars, where as in SW we have times in the books where Han has picked a piece of baseball-sized Neutronium up and crumbled it to dust in his hands)
B) How they interact is more about how do the races therein interact. Do we assume it is an All of ST vs All of SW slugfest, with every race and creature from both sides lining up to defend their respective universe? Or are we going to look at just the primary races? Do we consider that, perhaps, some races from either side would remain neutral, or even side with the other? Or that their could be random wildcards? Lets face it, the chances of the 'Vong or Species 8472 teaming up with anyone are incredibly slim, while the Rebel Alliance and the Federation are more likely to share information and technology with one another once they realize a common enemy (Empire). And the Borg... well... are likely to just be the Borg.
Also, what time period do we assume for both?
C) We know that HyperDrive requires pretty detailed starmaps in order to allow for jump plotting. We also know that Warp Drive, while able to be used without prior knowledge of the area, works best in well-documented "warp lanes" where the system can best warp space to permit the highest speeds (this is the explanation for why sometimes a higher warp factor can actually end up being slower than a lower one, even within the same SEASON). What kind of starmaps, tactical/cultural/political data, etc do these two universes get on the other?
D) Self explanatory - both sides have their "moments of derp" where physics goes out the window - do we want to just allow these for the sake of argument?
E) Again, self explanatory, but comes down to how we answer B. If we go, in B, with All of ST vs All of SW... then game over. Why? The Q Continuum snaps their fingers and bam, the SW universe is suddenly sterile from the start and no sentient race ever crawls from its primordial ooze. This one is tricky, especially because of the demi-deities in both (such as high end Force users in SW and certain entities such as the Traveler and Kevin Uxbridge (a Douwd) who can bend reality and energy to their wills). For this matter, do we allow the Force at all, and if so, how so? Do we go with the midichlorian explanation? Again, setting such ground rules will keep the debate fair and on track
