It'd seem druids don't have access to these themes from start-up. Many times druids favor one aspect of nature over another and will attune themselves to it so I think it'd be appropriate if they could pick one of these four themes to complement the druid's concept.
Having improved summons in general, without having to join a faction in order to access them would be nice too, aren't Druids thematically attuned with summoning spells anyways?
I agree with the OP. From creation, druids should be able to choose between:
- Default (Underdark)
- Rats
- Snakes
- Insects
- Spiders
- Earth
- Air
- Fire
- Water
I'd also see no problem allowing rangers all the animal themes to choose from... just a thought, for those rangers that might do some summoning with inspiring flavor. :)