One of the benefits of Improved Grab, is that you can attempt to hold a creature with only the appendage you made the attack before your free grapple check, by taking a -20 penalty, which can be alleviated to -10 with the Multigrab and further to 0 with Greater Multigrab feats. I'm playing an Anthropomorphic Octopus who uses this to make 6 grapple checks in a single round, dealing constriction damage on every one, and rending constriction damage every second successful tentacle grab. If you're talking Theoretical Optimization wise, you can instead use a an Anthropomorphic Giant Squid, and get 8 tentacles instead, at the cost of +1 LA on top of 2 Monstrous Humanoid HD. Next, are grafts. You can get at least 2 more pair of arms with grafts, for a total of 10 pairs of limbs you can make grapple checks with. Next, you splash Totemist to get Girallon Arms bound to your Totem, for 2 more pairs, totalling 12. You then get a wizard buddy to cast Blessing of the Girallon on you to total 14 pair of arms. Then you get your wizard buddy to also cast Arms of Plenty, for 16 pairs of arms. Not all of those arms can make attacks, though, so you can get him to also cast Fuse Arms to fuse those who can't with those who can, and you'll stay at about 12 pairs of arms, but with a massive bonus to Strength.
Sounds about good?