If your speed of development is glacial because the language you are writing in is just a hop skip and a jump away from ASM, then the language you are writing in is inadequate.
If your speed of development is glacial in C, then perhaps its that the skills of your developers that are inadequate.
This sounds a lot like some random FUD that you picked up somewhere. If C dev times are so long, why is it that new versions of large scale applications written C are available so often? An adept C programmer can get an application up and running in quite short order. Quick GUI? GTKDialog is available as are: Win32 GUI API, GTK, QT, ncurses, FLTK, and many more. It is also worth noting that should your customer/employer be willing to use some opensource code in his/her/their application, the amount of open source C code available online is quite staggering.