That would be stupid for many reasons:
1. It'd throw away a rare Senate seat that Democrats would likely need
2. It probably still wouldn't be enough to flip Texas, because Cruz has his own special problems that wouldn't necessarily be transferable in a Presidential race.
3. He'd be strung out as inexperienced, and rightly so.
I agree with the point about giving up a senate seat & probably not meaning TX goes Dem. But-
2 years in Senate & 6 years in House + 10 years as a TX state legislator ... isn't exactly inexperienced. (would be as much experience as Obama or Trump)
(or in Julian's case: 2 years in Senate, Cabinet Secretary, & 6 years as Mayor of the 5th largest city in the nation... even if a weak mayoral model).