I have had similar issues with brands- and the brand owners I have worked with have taken different approaches.
My feeling is this: if the brand is being led my the availability of a .com, one will not be true to the core vision of said brand. A TM is undeniably more important than a URL in my opinion. If you feel you MUST have the URL, then I would start from the beginning again, find an available name, check USPTO website for TM availability, then test.
A very smart strategic planner I know always said "idea led, consumer informed" - this is true and how I would approach it.
If the URL is not available, I would encourage your team to come up with clever, memorable URLS that all redirect to the mothership URL - things like cloud-like.com or yourcloudormine.com
There is no right answer, but brands are built one way-over the bodies of the people that work on them.