I am not a big enough follower of SW to make a recommendation for a story line for Republic Commando 2 but I have some ideas I would like to see.
1. Return of Sev - While on on a mission on Trandosha, they encounter a droid or Trandoshan carrying a Republic Commando weapon that seems 'familiar'. This raises question amongst the pod regarding the loss of Sev. Returning from the mission during their debriefing they are strangely granted 'leave'. Just so happens they are passing near Kashyyyk. (wink wink). Obviously they decide to 'drop in'. No prizes for guessing the rest.
2. I would love to see more non combative features in the game. Get to know the characters better. Perhaps things get worked into the storyline. Repairs/non combative missions ect where information is overheard and turns out to be good intel or something like that. This will help break up the 'boom boom boom ' action.
3. Extra combative interaction: How about some vehicles - especially air combat.
I would also like the option of perhaps capturing enemies instead of killing them. This opens up the idea of interogation - Could you include interogation into a FPS?
4. Include Wookies into your team. I would love to be able to include armed Wookies in my team at different stages. Have them as part of the team or instruct them to act on their own or as part of an independant group.
These are just my thoughts. I would LOVE to see a sequel. Especially if it remains true to the original.