now thats not a bad idea // jumps around of thinking about stomping on cylons with a madcat or atlas mech//
That would be cool. The Battle Tech mech should do well against Cylon infantry but would get there ass kicked in space. Basically a Cylon Centurion is just a more advanced mech in a smaller (thus less armored and fire power) chaise. The Cylons would always have a range advantage.
If I was to do a Fan fic cross over I would do it during the Clan invasion. Have the Colonel fleet come in from below (the opposite direction of the clans) and find a outer rim Fed Com world.
It would be evidently apparent that the IS powers were less advanced then the Colonel fleet (and in strange ways to) but still based on the same tech tree.
Like a jump ship has a crappy recharge rate and has to use a sail to recharge but has a 30 light year range compared to the Colonel jump range of about 10 per jump. But both would still use the same kind of FTL style.
In my fic I would have it that if they took a Raptor computer and jump engine hock it into a Jumpship so it would be able to monitor it recharge rate with its fusion engine (with no risk of it exploding). Making the jump ship able to make a jump every day instead of a week or more.
So the Colonel fleet could bargain with tech for aid. This would also help the IS get more advance before the Cylons show up. But when they do planets are going to get nuked and the IS kicked hard but its just to big and advent ally the IS would rally enough Old but modified to nBSG levels to kick them back.