Where have I seen something like this ?

[flywheel1935]

Anything is possible, just look at the supply of cranks, heads, blocks etc. but if you talk to our cherished suppliers you'll discover there is a significant up-front cost to these things (even if it is machined from billet someone has to draw it /redesign it first) and very few potential customers with pockets deep enough to justify it.

Exactly Peter, that's the one part you can't get off the shelf, however deep your pocket is.