It would be nice to be able to reverse poor relations, or even gain positive relations faster with other factions through opportunites to garner favor.  


This could be done through quests, specific resource gifting, or special system build options that come periodically. A system build option might be something like "This turn, your systems can observe a Hissho holiday to garner favor." 1turn


I got this idea when I went from war with an alliance to a truce, with no real options to join the alliance any time soon after the truce was over.  I'd rather have a path to joining the alliance through diplomacy as opposed to probably going to war and wiping their existence from the galaxy.