No, the President shouldn't be able to borrow whatever he wants.
The debt ceiling mechanism might be an unnecessary anachronism and I'm not necessarily against doing away with it, but if nothing else, it can serve as a useful reminder to people about our ever-increasing debt. Maybe we should require a super-majority in Congress to approve any deficit-expanding appropriation instead.
"I'll see you guys in New York." ISIS Caliph Abu Bakr al-Baghdadi to US military personnel upon his release from US custody at Camp Bucca in Iraq during Obama's first year in office.