Id like for the pacts to change the weapon type of your LRFs for example. Like if you get a beam pact, your lrms fire beams! but still benefit from your own missile research. This would be cool.
You know, this makes me think back to Red Alert 2 where, if you got a spy into an enemy battle lab, you'd get access to a mixed technology unit; for instance, if you were an Allied nation, getting a spy into a Soviet battle lab would unlock Chrono Ivans.
What if these pacts could do the same? As examples, getting a beam pact with an Advent player as TEC would unlock beam cruisers, getting a missile pact with TEC as Advent would grant you cluster missile destroyers, and Vasari with the TEC siege pact would get a sort of micro-capital ship; a multirole heavy cruiser that can bomb planets and effectively fight other ships.
Of course, the balancing would be a bit nasty and the workload would be a bit heavy (Were my basic examples to go through, that'd be nine new ships, three for each race, which may well be more than Entrenchment had to offer), but I say it'd be worth it.
Although, I seriously doubt this is going to be implemented. I just figured I'd throw that idea out before I went to bed.