Pets would be cool, but why stop there?
Why not have playable Varen character kits?
I know, I know on the surface it sounds stupid, but remember that DA:O had the Mabari companion that players could control, so its not like having player controlled, non-biped characters is foreign to BioWare.
I could easily see an 'Alpha' Varen class running around with the other players. Such a class obviously wouldn't be able to use guns, and would rely on melee attacks, but the advantages would be a smaller, harder to hit target for enemies, as well as its attacks ignoring shields, or something to that effect. Plus not being able to climb lasers or use cover is not anything new to the MP kits.
For lore reasons why medigel and ops survival packs can still be used, just say that the Varen is wearing armor with a VI installed to administer stims in battle.
It could be bart of the "Alien" DLC pack which would include playable Varen, Rachni, Hanar, and Elcor.