Do you have access to any type of unit that could be held in reserve/outflank/etc?
Alot of forces have something like that with the stipulation of "Must be brought into play by the end of turn/movement phase x or count as destroyed".
If so, pay the points for them so you hit your 1k pts, put them in reserve, & simply never bring them into the game. Thus not really needing to have finished models for them right at first.
Plus I doubt people would mind fighting
less Ossiarchs.... Though it might make winning the initial matches harder on you.