I was wondering the same thing, as I have 25 assault marines that I can't be bothered to plunk on ebay and have been thinking of ways to turn them into a Ravenguard allied detachment to my Salamanders. I want to stick to fluff for both so thought RavenGuard could provide all the fast attack units my Salamanders lack so would compliment each other nicely.
I have thought about using this guy: http://www.forgeworld.co.uk/Warhamme..._KORVYDAE.html
since all my games are friendlies and non-competitive.
He makes Assault Squads troop choices, but you must take a scout squad with land speeder storm to unlock this, which to me is fine since I wanted to run that unit anyway.
His rules are in IA8 and he is a reasonable 160pts, comes with iron halo, TH, melta bombs, krak grenades and that unlock ability. Perhaps an option if you play with people who are fine with FW.
If not then Shrike seems like an auto include (though is a tad pricey). Then I was thinking of Vanguard Veterans either a 5 man or full 10 man squad depending on size of the game, with 2 or 3 storm shields and perhaps a grav pistol. Nothing else though, because that alone is expensive, and when tooled up with dual lightning claws or TH/SS they become insanely expensive...Then of course infiltrate them with Shrike.
I think x5 Vanguard with jump packs, x1 grav pistol and x2 storm shields comes to something like 160pts.