What stalled the trade was Scott Kazmir. The Mets wouldn't mind unloading Heilman for Soriano, but the Rangers wanted Kazmir, who is as highly touted as any arm's been in the Mets farm system in a long time. NY decided it was unwise to give up an arm like that, even for Soriano, who I should point out to whoever said the Rangers aren't asking enough, is not as good a real life 2B as he is a fantasy 2B.
The Mets went into talks saying Reyes was off the block, so I don't think he was an issue. Initially when it looked like the deal was going to happen, the Mets major concern with Soriano was if he could make the defensive adjustment to the OF quickly enough. With Kaz and Reyes, the Mets have one of the better young defensive middle infields, and throwing Soriano in at 2B would certainly change that.