any pilot can try and start an association should he or she feel there is a need.
Should a union become the result, it not only affects those that voted for one, but also drags in those who are opposed. Once there is a majority vote, the non union supporters are now union as well and now must follow the lead from their pro union counterparts. Thank goodeness for voting on everything after that, but you can see how a small percentage difference of people can have a huge impact on the others lives as well (example 51% yes, 49% no). A 5% raise to some might be good, but may bump someone into a higher tax bracket and thus be a net loss for them in the end.
As for engineers being affected by pilots creating a union? Damn right they will be affected. Firstly, concessions made by employers to cover the new higher wages, may be taken from one pocket to fill the other. As well, when the pilots go on strike to get what they want, it would dictate the aircraft are now grounded and the engineers livelihood is now taken from them. It affects us, and I will stand my ground, ask questions when questions arise, pressure those when pressure needs to be applied. How could you allow someone who crumbles at the first sign of opposing pressure to be the leader of your pact? If they can't stand the heat how would they handle negotiations?