Seeking fun feats for a melee Goliath Druid / Hellknight Signifier

[Abraham Z]

Please give me some suggestions for feats that would be appropriate for this build.

Oread LN
STR 18
DEX 12
CON 14
INT 10
WIS 17
CHA 5

Traits:
Earthsense (Oread racial, gives tremorsense 1/day)
Reactionary (+2 init)

1. Goliath Druid 1
Feat: Warrior Priest (prereq for Hellknight Signifier)
Domain: Animal
2. Goliath Druid 2
3. Goliath Druid 3
Feat: ???
4. Goliath Druid 4
- gain Animal Companion (Elasmotherium)
- gain wild shape
5. Goliath Druid 5
Feat: Boon Companion (Elasmotherium is now fully leveled)
6. Goliath Druid 6
- gain wild shape into Large humanoid (giant)
7. Hellknight Signifier 1
Feat: ???
8. Hellknight Signifier 2
9. Hellknight Signifier 3
Feat: ???
10. Hellknight Signifier 4
11.  Goliath Druid 7
Feat: ???

Basic (rp) idea of the character: He's a druid in order to "tame" the wildness of nature and bring some order to it. Wants to get the plants to grow in neat orderly rows. He's also hunting for his family dog, who has run away - he joined the pathfinder society because it provides the best chance to go all over the place and look for the dog.

Basic (mechanics) idea of the character: I expect he'll be mainly a melee druid, relying on the ability to keep your weapons and armor when you wildshape into humanoid form to have fairly potent offense/defense while wildshaped and to team up with his AnC (Elasmotherium) to do some damage as melee frontliners, both with reach. Of course he'll also have some casting as needed, but I expect a lot of this will be for buffs or utility. I don't plan to wildshape into non-humanoid forms except when really needed, so I'm not planning to take Natural Spell. I also don't expect to do a lot of summoning, so I'm not planning to take Augment Summoning.

Being a Hellknight Signifier is mainly for fun rp (I like the combo with druid for hilarity), but it does keep my spellcasting fully leveled and because my AnC comes from my Domain, the Hellknight Signifier's catechesis ability will keep my AnC fully leveled (as long as I take Boon Companion to make up for the fact that the Domain AnC starts out 3 levels behind). I also gain heavy armor proficiency, proficiency in my order's weapon (not sure which this will be - I'm tempted by the lance and the idea of riding an Enlarged Elasmotherium, so my Large giant form riding on the Huge AnC, but I suspect this will be impractical most of the time in PFS).

So, two of my feats are spoken for: Warrior Priest (needed for the Hellknight Signifier prereq) and Boon Companion (to get my AnC up to full level). But otherwise I have no idea what the rest should be (i.e. levels 3, 7, 9, and 11). I know I could take some of the old stand-bys like Power Attack and Improved Initiative and Toughness, etc. but I'm more intrigued by building towards something more "fun", but I'm not sure what that might be. Any ideas? Maybe some Teamwork feats to work with the AnC? I'm considering Totem Beast at level 7 to boost the AnC's STR.

By the way, I've already played this character at level 2, so my basic stats etc are fixed.

Many thanks in advance for any suggestions you may have.