Yes, I agree. Your ignorance would lead to to incorrectly call those changes the easy part.
I cringe at having to explain this:
There is an engineered balance between the position of the feed ramp for reliable feeding, and the position of the rear of the spring to ensure the spring is not collapsed during recoil.
Inside this space, a locking block and barrel lugs must be arranged such that geometric constraints (space) dynamic constriants (sufficient space for the barrel to move straight back before it begins to fall in unlocking to permit time for the bullet to leave the barrel), and strength constraints (the locking block must not break, therefore it must have a certain amount of material in it.)
Once you have designed one gun, say, the G17, you have done a mass of careful calculation and design woork. In order to change these geometric, dynamic, and strength relationships while ensuring a successful design, you must do all of that design and calculation over again. All of it. You must go through the expensive prototyping process again, from scratch.
To shorten a grip, you must cut it. That's all. No strength considerations, and no dynamic considerations. Hell, with a Glock, which is unique in having a block to stoip the magazine going too far, you can even cut the grip far too short and it will still work.
So, go back to reading a gun rag and thinking it tells you something useful about the engineering involved in firearm design.
Sheesh.
As far as the finger grooves, put them wherever you want! Their positions have no engineering consequence. It's just a set of injection molds, and the manufacturer needed to make a new set of those for the shorter frame anyhow!
PS: When you find yourself in a hole, stop diggin'.