A potential way to assemble a Contraption.

Hmm. That seems to actually work. Not sure it's Johnnyish enough to be worthy of the Steamflogger legacy on its own, but it does actually work which has to count for something.

Must resist the temptation to start discussing Prismatic Gaslamp and Junk Harvester again...

ROFL! That does fulfil almost all of the necessary conditions.

Does it also need cards that actually assemble stuff, eg. a rigger creature with "T: assemble target contraption" or even adding "tap an untapped creature you control: assemble this" to the contraptions?

I'm not sure if it's possible to make the assemblage interesting without being parasitic. Maybe "tap an untapped creature" is the way to go, but riggers are creatures which typically interact with contraptions in some other way?

I agree it's a shame it's not more Johnny, but it could be, depending what riggers do, and even though Steamflogger sounds Johnny, I'm impressed by any mechanic which makes sense out of it, and I like this one quite a bit :)

PS. Although, doh! Maybe assembling needs to be a property of riggers so haste speeds it up?

I posted several cards inspired by this variant of assemble in "Cards with No Home".