but then he makes that same point every time. Maybe that's why he's writing instead of engineering hardware.

"get rid of the delicate silica and carbon-carbon thermal protection system and replace it with a robust titanium thermal protection scheme"

I haven't been following thermal protection recently, but if you're going to do this why not do it on a new design? The cheap way to do this would simply be to restart the X-33, particularly since the tank problems have been solved.

"big dumb rocket motor like the F-1" - there's nothing dumb about the F-1
what the big dumb rocket has is pressure fed liquid propellants

"The gotcha is convincing the political system to pay for the development costs."
Fundamentally, stop living in the past. Mars is noty Earth-like, and that means moderate launch demand, and no money for development costs.

If you want to lower costs, design your mission modularly for use with extisting EELVs - that way your mission costs are lower, and your mission is cheaper, because it lowers the cost of the EELVs.

see, for example:
http://www.geocities.com/epgrondine