11-dimensional M-theory has N=8 supersymmetry, and N=8 supersymmetry is observable only at very high energies; Usually, N=1 supersymmetry, or "minimal supersymmetry" is considered the most "natural" amount of supersymmetry in string theory.
The formulation you propose, would be fact exactly equivalent to M-theory, and would also have N=8 supersymmmetry. In general, compactifying on a class of manifolds known as G(2) manifolds (the 7-dimensional counterparts of Calabi-Yau manifolds) reduces the supersymmetry of M-theory to N=1.
So, well, yes, you could derive a 4-dimensional theory related to M-theory by a series of T-duality relations (this is absolutely wrong, as 40227 points out above) but it's going to have N=8 supersymmetry, which is not exactly an ideal solution.