One of the bigger problems I see here is not having access to a local development environment. If you will be traveling and attempting to work remotely, this might be even more important - as I have found with my last year on the road that hotel and coffee shop wifi is not as reliable as you would hope, and losing development time due to a 6hr plane ride (without wifi) can really be an interruption. You must be fully aware of what it means to rely on being connected 100% of the time.
Granted, with the right tablet, and the right amount of work, I’m sure you could stand up a workable environment, and in the absence of connectivity, find some tasks that will be valuable.
When comparing a tablet to an ultrabook as a primary development device, I only see drawbacks. Maybe a Surface Pro is in your future