[BlitzKrieg]

How about cross career benefits?

Level 5 in both medical AND Science and you can make the cheapest Borg implants (and implant them) at 1/10th cost

Levl 10 you can make the mid level implants and implant them at 1/10th

Level 15 in both and you can make the best borg implants at 1/10th?

For a house I'd say you'd need 5/5 manufacturing and construction to build the houses in Downtown
8/8 to build the industrial
10/10 to build the next
15/15 to build the next and
20/20 to build the next...