There are already oils out there that would qualify for this viscosity rating, IF it existed.
Look at the specs on different 10w30s for instance. One will show a viscosity of 9.8cst at 100c
(Mobil 1) while another shows 11.9cst at 100c (Amsoil) Both are technically 10w30, however
the Amsoil is almost a 40wt, while the Mobil 1 is almost a 20wt. So if you want a thicker oil,
look at these specs.