I would think it likely that an attempt to assassinate Assad could well have the reverse effect, and rather than impeding military activities could serve to escalate them, even if it disrupted them.

I cannot see how any plausible military intervention could have any significant effect in reducing civilian suffering in Syria, rather than the reverse (as happened in Iraq). Basically it would be a political gesture for internal domestic purposes. Public relations.

The same sequence of events seems to be operating as in the build up to the Iraq War. Demands for inspection, followed by the claim that inspection is inadequate, followed by escalation before the inspection has been carried through, and a rush to war.