Oops, forgot that prereq.
We can drop Snatch in favor of something else, but we need Imp Bull Rush if we're keeping Awesome Blow, which I always like for big monsters. I'm also not very fond of Imp Natural Attack, as we're allowed to set the damage values as we like --- since we're giving different stat blocks, we're not set to the size advancement rules for damage. Here are three alternatives, one with Cleave/Great Cleave and two without:
I'm not sure it'd have much use of Awesome Blow, since its signature attack involves engulfing opponents in its body rather that hurling them away, but I'd be OK including it if you like it.
Normally I'd agree with you on the Improved Natural Attack, but in this case it's a legacy issue - all the officially published Elemental Monoliths have the feat, so I think we should give it to the Quasi Monoliths too, like we already have for the the
Dust Quasi.
Weapon Focus (slam), Weapon Finesse, Combat Reflexes, Alertness, Iron Will, Lightning Reflexes, Power Attack, Cleave, Imp Initiative, Great Cleave, Imp Bull Rush, Awesome Blow
Weapon Focus (slam), Weapon Finesse, Combat Reflexes, Alertness, Iron Will, Lightning Reflexes, Power Attack, Imp Initiative, Imp Bull Rush, Imp Sunder, Awesome Blow, Imp Natural Attack (slam)
Weapon Focus (slam), Weapon Finesse, Combat Reflexes, Alertness, Iron Will, Lightning Reflexes, Power Attack, Imp Initiative, Imp Sunder, Imp Bull Rush, Awesome Blow, Dire Charge
The Weapon Finesse shouldn't kick in until Large size, since that's when the Dust Quasi's Dex bonus starts to be higher than its Str bonus.
Let's see, the SRD Earth Elemental goes:
Small (1): Power Attack
Medium (2): +Cleave
Large (3): +Great Cleave
Huge (6): +Improved Bull Rush, Awesome Blow, Iron Will
Greater (8): +Improved Sunder, Alertness
Elder (9): +Improved Critical (slam)
Monolith (13): +Improved Natural Attack, Improved Overrun, Toughness, Weapon Focus (slam)
If we kept the Alertness, Iron Will, Improved Bull Rush, Critical and Sunder in the same size categories, that means we'd have to put the Power Attack in Medium (since it's Small Strength is too low to match the prereq).
It might be better to move the Awesome Blow and its prereqs to a later size, so we can space out the "speedy" type feats in front of it.
We've already decided to move Weapon Focus and Finesse to near the front, and I'd like to keep Imp Natural Attack were it is.
Come to think of it, if we're making this "Ref strong" like an Air or Fire Elemental, shouldn't its Weapon Finesse and Improved Initiative be bonus feats like the SRD Air and Fire (except for the Monolith).
Putting that together, I'd go for the following:
Dust Quasi
Small (1): Improved Initiative (B), Weapon Finesse (B), Weapon Focus (slam)
Medium (2): +Power Attack
Large (3): +Combat Reflexes
Huge (5): +Cleave, Iron Will
Greater (7): +Alertness, Improved Bull Rush
Elder (9): +Awesome Blow, Improved Critical (slam)
Monolith (13): +Improved Natural Attack, Great Cleave, Improved Sunder, Improved Initiative