I have three thoughts:
(1) It looks to me like molasses is only about 50% sugar, so I would use twice as much molasses as priming sugar.
(2) I don't think that the flavor contribution from molasses, used in quantities appropriate for priming, will be noticeable; I have certainly never found honey or belgian candi syrup to be noticeable when used for priming.
(3) I also think that getting the molasses to completely dissolve and uniformly mix in the beer will be difficult, leaving you with some bottle bombs and some flat bottles. Given my (perhaps totally wrong) prediction about the limited flavor contribution of priming molasses, I wouldn't take the risk of ruined bottles and personal injury.