I have a significantly higher opinion of Booker than you do, but then his Technocratic leanings are a plus for me. His tenure as Mayor of Newark makes me see him as one of those old-school practical liberals who knows how to keep the far left at bay, while improving the quality of life on the ground. They tend to do really well in big cities. Eric Garcetti is another one in that vein.
I don't view ambition and self-interest as a real character flaw, more a prerequisite for jumping into politics.
My only real issue with Booker is his rather strident veganism.
I also hold Booker in high regard. He is one of the few Democrats who uses intelligence and creativity, rather than trite moralistic arguments, to move an agenda. He also seems to understand that real political power is derived from making things work, not from getting your way. He's like a socially-liberal Paul Ryan or a practical version of Rand Paul.
If he runs in 2016, I'll vote for him. He'll only be 47, and a bit short of executive experience, but he'd win in a landslide, imo.
