So need some advice. So far I have 8 marines with different options for use in sternguard and command squads as veterans. They are also interchangeable with my tac squads as sergeants. Here's what I have:

2X Combi melta/power fist
1X Combi flamer/power fist
1X plasma gun
4X bolters with drum clips (for sternguard)

So the issue is I've got 4 more marines to make and can't decide what the weapon options should be. Any ideas for good flexibility?