I guess that really screws the carbon dating model too....
Nope. It does not affect it in the least bit. C-14 does not equal U-235. They have no affect on each other.
If you are referring to the relation of the natural abundance with time, C-14 does not operate on the same mechanism that U-235 does. The C-14 abundance is relatively constant because it is constantly produced in small quantities in the upper atmosphere. Since it only has a half life of ~5700 years, none of it could have remained even if 100% of all carbon at the formation of our planet was C-14. Contrast this with U-235 that has a half-life of 700 million years and no mechanism of production (it is formed in supernovas or other significant stellar events). Obviously a significant fraction of U-235 remains even after 6 half-lives (which if you do the calculation is about 1.5% of the initial abundance). Try the calculation with the half life of C-14 if it had no production rate (~800,000 half-lives--hint: you won't be able to use most calculators to find a value this small).