Nice work rafael! If you could now move those faces or face according to a falloff that would be a very powerful tool. Let’s say you picked the centre face of your selection and moved it up, all the other faces would move by a proportional amount down to 0 at the outside face. This might only work with quads but you could create domes, spires, depressions etc.
Planning to build powerful modeling tools like the one you described, but in the meantime, I recommend the following Extensions which I personally use and can attest to their functionality & quality. These two plugins can do a similar task of what you just described and more…
Yes, sometimes ShrinkGrab leaves edges behind that shouldn’t and I am currently thinking of ways to solve this. For the moment all edges are removed from selection if no faces are in selection.
In Grabby 1.0.3 (I know, it’s not the latest version, but refering to its animation above) I see two selections growing. What happens if they happen to overlap when growing any further? Does the extention deal with such cases properly, both in increasing and in decreasing the selections? I can imagine ‘ShrinkGrab’ would ultimately be dealing with just one selection → to zero. Just a thought