In theory, it should work. In practice, it's up to someone with endurance through lots of experiments.
http://www.bagend.com/bagend/downloads/E-Trap.pdf
E-Trap might be one of the solution for fighting room modes. However, I doubt it for the mic-picking method of detecting room modes (live-feeding?). Filtering with EQ upon the source line is of course OK, especially for damping the positive feedback such as micking inside of an auditorium. It is the cheapest method also when applied to fighting room modes at home. The most costly method might be recruiting bass traps that work with very large amount of space and acoustic materials.
My suggestion is simple. However, anyone has the idea why it won't work at all? Or, why the E-Trap not known to the world? There must be some weak points here.