Having impact two different traits could be a balancing nightmare taking years of work to fix (if ever).
I suggest that they simply be better and MUCH more costly version of the existing options (similar to how faction items are better and much more expensive than T2 items and only effect the same attribute).
I realize that CCP has put things into the game that effect 2 traits like the ballistic control that aids both missile and drone damage and EVE didnt explode. That being said, the outcome of suddenly and significantly changing all rigs to have dual purpose offerings could in fact explode EVE.
When all is said in done; however, im against them as a concept and only put forth the above suggestion to further the conversation and propose a compromise if they do get put into the game.