Actually, if one absolutely HAD to have Riker and Troi on the show, then it would have worked better post-Nemesis. After the events of that movie, Riker and the Titan were assigned to help Romulus after Shinzon's coup. They could have written a finale something similar to what Jarod mentioned, that they find the NX-01 wreckage on Romulus and start doing research about how it got there.
For that matter, changing the setting to something just after Nemesis while not changing the rest of the story would have been fine, as then it could be about Riker and maybe Troi processing their grief at Data's ``death'' by studying Tucker's.


