Above all, RGT is one more evidence of the current FIA practice of restraining rally car building to manus official tuners. It's true they've allowed private tuners to homologate GT cars, but the system is too hard and expensive, that's why it failled.
I've reed the previous pro and cons remarks and like some of you I found some current GT's too bulky and overpowered for rally (I got 'traumatized' by JP Fontes Aston Martin V12 portuguese outings), but also as many says there's need for more diversity in rallysport.
With proper regs (limited cubic capacity, external dimensions, overall weight, etc) and easier homologation processes, GT cars as the Cayman, the 4C or the new A120 could become suitable alternatives in those countries that got all tarmac rally series. They even doesn't need to be winning champs machines, as they are entertaining enought to drive (and watch) and can get reasonable runing costs (Vallejo spend half of an R5 budget with his 911, during Spanish championship).
Btw, some GT drivers has proven that they aren't only straight fast:https://youtu.be/1Za0gkw3tSI?t=67