it's possible to force install FCP even into the white macbooks.
At the end of the day, the hardware would slow down everything to a crawl. An external 7200rpm hdd for scratch is advisable, but it wouldn't aid much in rendering. The graphics card is pretty minimal on the lower macbook pros, thereby your mbp would take hours or days for rendering HD video. It might be a bit easier working with SD video.
hope this helps