A couple of thoughts.
First, this stuff is truly excellent! Very creative, very inspiring and very, very well executed. I look forward with anticipation to seeing these little guys lined up and painted on the field. Thank you for sharing your work.
Second, Devilfish. not easy. The MTT transport is the most obvious choice, but to do it to scale would make it far too large for game purposes. It should be used for a special carrier in apoc games, maybe a firewarrior Orca? But what about a Battledroid Troop Carrier?
Here is a link to a website with technical drawings of starwars vehicles of all sorts:http://www.dorlingkindersley-uk.co.uk/static/html/features/starwars/technology_gallery/index.html
There is a good picture of the Carrier on page 1, and of the MTT on page 3. It is about the right size, and carries a number of droids closer to that of a Dfish than the MTT does. While it looks like it should be open topped, this shouldn't matter, maybe since it is droids its 'open topped-ness' is negated.
As mentioned above, you could make the droid racks out of Railgun halves for the long piece, sprues for the little arme that hold the droids and the two Dfish doors for the plates at either end of the rack. The bottom plate of a Dfish chassis with the droid holders cut off could be made to work as the base for the carrier with a bit of work, and the front plate on the carrier is close enough in shape to an upturned Dfish nose with the drone holders removed, or even a Piranha nose. While the Carrier does not seem to mount any weaponry, adding a BC shouldn't be a problem, and whatever you use to represent drones in a droid army I'm sure they can be made to attach somehow without altering the design substantially.
Third, a commander. Grevious is a fantastic idea, and I look forward to seeing your monowheel conversion, but another idea could be to make Count Dooku on his Speeder! There is a nice picture of the speeder on page 2 of the linked webpage, and the speeder's similarlity to a jetbike would make a closer approximation of the suit's JsJ ability.
One more thought would be to use the design for the droid gunship on the same page for a skyray!
Anyways, now I'm getting carried away... but I look forward to your updates!