Can you explain which concerns, and why they cannot be addressed? Why would using another port than 8333 be less secure?
I'd say using a fixed port has security/networking problems of its own.
My concerns are more along the lines of potential for DDoSing the network if you have infinite nodes (well 65000 per IP) and sybil attacks. But those are mostly because I haven't read enough of the networking code to realize all the possibilities (nor do I think anyone really has). If you spend enough time reading up on net.cpp and can convince people that those aren't a problem, then I'm sure it would get merged.