Do you feel like some modelling? I think you may be able to use a command box set to make the bikers into a command squad on bikes, this is a really solid choice. The models i.e. apothecary and banner are solid choices in
DA codex now as well.
I would run the bikers as 4 bikes with 2 plasma with an attack bike with
MM. Usually I want them scoring or
BA so they can get some
FNP.
The terminators are not that great. What does work is putting 5 in a land raider and then have 5 with 2 assault cannons.
Plasma weapons are really useful but just not versatile or needed as much as any other weapon.
Stormtalons are usually needed rather than good.
The next purchase should be two razorbacks, this gives a lift to the librarian and they can roll behind the terminators to get cover saves.
Then storm talons work better in pairs. I wager it will not be in the new codex