Hiya,
Just a suggestion, Basically I think that transfer units are too 'expensive' compared to the other industry items. to cut a long story short for the resources consumed by building one transfer unit you can build either 1 medium container, 1 large engine a large assembler or 5 other industry items. Personally i don't believe the limited functionality of the transfer unit when compared to the other items in its 'category'.
Building and using transfer units would be much more appealing if they consumed just as much resources as as single medium industry maybe even 2 at a stretch given that they seem to be a hybrid industry unit/quality of life asset. currently their primary function seems to be to pick up catalysts from the out tray and place them back into the in tray....A large Engine it is most certainly not....
thats all for now
UKFatguy