one of the recurring problems from a story perspective on the series was that it made no sense for the first officer of the prized ship in Starfleet to go on so many heroic mission and have so much success and not actually become the captain of his own ship. It was stretching the point to incredulity that Will Riker would not accept a ship of his own where he would be the Captain.
So, according to the commentary tracks on the third season of “Star Trek: The Next Generation” on Blu-Ray, the writers initially considered killing off Commander Riker and then having Lieutenant Riker (whether he would call himself Will or not is up for debate) join the crew, with Commander Data becoming the new first officer for the ship and Riker taking Data’s old job as the head of operations. It would explain why Riker wouldn’t leave the ship, as he would now be at a very different point in his career. It would also create all sorts of new dynamics, with Data as first officer and with the other Will re-meeting all of the crew of the ship and presumably he would pursue a relationship with Troi again.
However, the main issue was this was late in the show’s run, and they had been discussing a film version of the show for some time now, and it just seemed like a bad time to drastically alter the framework of the show, so the idea was scrapped.
A few years later, then-“Next Generation” writer Ronald Moore made the same proposal for an episode of “Star Trek: Deep Space Nine” where Colm Meaney’s Miles O’Brien was replaced by a sleeper agent replicant.