Weight training to develop the strength needed for takedowns. A suggested rep scheme of a heavy weight for 6-12 reps since any less will spark the growth of fast twitch muscle fibers which will fatigue faster. You are training your client for fighting, not bodybuilding so incorporate the push/pull method because in fighting you strike (push) and grapple (pull).
Personally I feel that although important, weight training isn’t a priority. Muscle mass will make for a stronger athlete but if the athlete lacks technique it won’t matter in the ring. The best exercise routine for MMA takedowns is to do them via partner training.
Similar to stand up, when asked how do you improve your kicks & punches? – you practice kicking and punching!
Also no one mentioned cardio! I mean after all the one who tires first becomes the loser.
Here is an article which you might find interesting on training the MMA athlete using the ACE IFT Model