features such as add-friend are disabled to the opposite faction because you can invite people in your friendlist.
So, if they were to enable this (and I honestly think they should) they need to make it for communicational use only. So you could see if your friends are on their alts of the opposite faction.
Grouping the other faction however, is an honest "no-way" from me... it would be awesome though, but then it removes the use of open-world PvP which they're trying so hard to balance right now.
Even if you could make it like 1 player from the opposite faction joins your group and make both of the players neutral..
Would this mean they can both be attacked by the two factions?
Can both of them attack the two factions, or is it just one person who is being attacked and the others can't do anything about it?
What would happen when you want to quest together, do you have acces to quests of the opposite faction? <-- this answer is obviously a no XD
it requires much more time and thinking through than you might suspect..
yes, it would be fun to do missions together since the objectives are the same, but grouping outside of the missions has no meaning.
Even if you are just trying to help a friend with his quests by using a character from the opposite faction, you can't just walk in places which are owned by the opposite faction.
You can't just stick to his side all the time..
Cross faction grouping would have to be strictly instance specific for it to work right. You shouldnt be able to have a jedi n sith running around together fighting mobs whether on PVP or PVE servers. Thats just sick and wrong!
I have suggested before in the suggestion box that we have cross faction flashpoints or ops. The story plot of a greater immediate threat that could cause republic and imperial strike teams to temporarily work together for a common benefit is already there. Directive7 and False Emperor come to mind...