You're missing one big factor here.
A Business has to make money. The largest demographic purchases AK's and M4's. By cutting the largest demographic and feeding into a niche group, you will have to charge more to meet the upkeep. M4's and AK's pay the bills. There is a reason they are so prevalent, and it's because they're the bread and butter of airsoft.
The second issue you'd run into is Licensing fees for your niche guns. These are very specifically designed weapon systems and, as such, have strict trademarks. Legally, you cannot just start pumping out Tavor's without obtaining the license to do so. It is an infringement on Trademark and most likely will result in cease and desist orders. If you do pay the licensing, you'd probably have to sell the guns for a ridiculous price tag just to pay the cost of licensing, never mind the previously discussed upkeep.
Any idea is a good idea, but very few of them are executable.