Cut back to MOMF3 or MOMF 2 (all you really want is Giant anyway, although Fey can actually be tempting, but not for a BSF). You will also have noted that the MOMF (as well as the Warshaper) has the same inherent suck programmed into it as the Daggerspell shaper - namely that enhanced wildshape does NOT stack with druid wildshape for Max-HD and duration. How many Gargantuan 10HD creatures do you know? Personally I think this is a really in need of a house-rule. Without a House-rule, get back as many Druid levels as possible. That also most probably means cutting back Warshaper to 2 levels. Keep the Beastmaster so he can keep the T-Rex.
So the build would look like this:
Druid11-x/MOMF2/Beastermaster1/Warshaper2;Barb or Fighter x (may be 0, I guess)
What I would do:
Pick the meanest Troll form he can get with the max HD allowable (WAR Troll requires MOMF3 AND Druid 12, unless the Accessory update changes it to Giant type). This is also the minimum Druid level you need to stick with. (Is there such a thing as a Practiced Wildshape feat? I don't think so.)
Then always cast extended Enhance Wildshape for Ex-abilities. That will take care of most defensive needs, the remaining being to get as much resistance as possible to the elemental damage that can still damage him.
Offensively there are two possibilities: Melee or Ranged. Since unfortunately his classes have eaten a lot of feats, a good offense will likely as not require a level or two of Fighter. Personally I would seriously consider ranged, since it only really requires ONE feat, Brutal Throw. Power attack is a given for any fighting character, and if he can fit it in, Power Throw. Now all he needs is items. (You can use Weapon Crystals for Quick-draw and Returning properties.) The trouble with ranged is his low number of attacks due to low BAB.
The melee variant undoubtedly needs Shock-Trooper and Pounce, so likely needs Lion Totem Barb 1 (if not going Cave Troll) or Fighter1. He'll be going with a smaller Troll-form, Cave Troll seems the best. He also wants a big two-handed weapon in reserve in this case, perhaps a reach weapon. (Strongarm bracers and one size larger than the troll form.)
Of course there is also the monkish-route:
Monk2/Druid8/FOTF1/MOMF2/Warshaper2/Beastmaster1; Enough for normal Troll shape, or just a Fleshraker. Cave Troll at Lvl 17 with Druid 9. This is very strong defensively, but lacks the ability to cast the better Bite spells - which seriously cuts down the damage unless he uses Venomfire.