it was contrived yes, but once you rule out time travel, it's either plot contrivance or a really old Kirk meets up with Picard in the TNG era as your options.
A much simpler contrivance would be for Kirk to be frozen somehow and revived. I think the Nexus was an idea to hard for them to make into a good idea. A random energy ribbon that causes disruption is a good idea. How about the Enterprise D discovers the ribbon about to threaten a colony in it's path, Veridan 3 if you like, and when Data's plan to dissapate the ribbon works they discover a body that was preserved and brought aboard, it's Captain America er no it's Captain Kirk! He's revived with Dr. Crusher's 24th century medical ability and the strange properties of the ribbon. After a short while, Data detects that the disruption of the ribbon is causing a different type of phenomena which is causing a possible disruption of the fabric of space which will cause a much worse, destructive decomposition of the space in the sector itself. Because Capt. Kirk is saturated in the energy of the ribbon, a way to prevent the formation of the new event is for him to enter it, but it will kill him. The crew of the D struggle valiantly to resolve this by any other means at their disposal, but Kirk resolves to solve this himself when efforts fail, he knocks out everyone but Data who assists him into a shuttle which he then flies into the forming disruption, thus ending the event and saving all the planets in that quadrant. The D holds a ceremony honoring his sacrifice and we go on our way.