Add the tripping tail sweep (like a Megalania, right?) and switch Improved Trip for Improved Disarm or Eyes in the Back of the Head from the SRD Divine feats?
Improved Disarm goes with Combat Expertise nicely, but there's definitely something appealing about Eyes in the Back of the Head. Hard to decide. I guess Improved Disarm, since presumably that also helps out any allies also.
Tail sweep usually deals automatic tail slap damage. Do we want to give the serpent lord a tail slap attack, or just have the tail sweep deal damage as if it had one (2d8 is typical for a Gargantuan creature)?
So would the full attack line be "bite and tail slap" or "bite or tail slap"?
If we go with the standard 2d8 damage for its size, they'll be identical, so once wouldn't really be a preferred attack mode over the other. Do we want it to favor the bite?