Thats a good question... I usually add Hogue Handall finger groove grip sleeves to my P99s. Could that be considered a 'modification'- I don't know. In theory, I could see Atty X making the argument, 'you have modified the stock P99 so you could shoot my client easier with that rubber sleeve.'May I ask, is the grip feel of the P99 so bad that you simply can't live with it unless it felt like a PPQ frame?
According to a discussion I had with a local instructor who has won an Emmy for his segments on the nightly news here, modifying defensive pistols is a bad idea. I was told, by him, that after a defensive shooting, it is not unheard of for the pistol used to be sent back to the manufacturer for inspection, to see if any alterations were done to the pistol. Do you really want this as a possibility if you ever have to use this hybrid pistol defensively, and all so that your grip can feel just a little different than a P99?
My argument is-its about a better grip for me. I've only upgraded the frame. I may have a touch of arthritis, I have 'improved the grip' w/o a grip sleeve with a PPQ frame. Yes- we are possibly splitting legal hairs here.
Re; Modifying a defensive pistol is a bad idea... Could it be considered "not changed from the 'factory' function of trigger, sear, etc." VS. 'Modified' by setting a hair trigger or hammer or etc. etc. That to me is a definite no no for a defensive pistol. Yes- it could be considered not 'original' now but also not turned into a race gun.
Just my $.02.
The simple fix is for Walther to produce a P99 M1 and M2.
I guess I forgot to mention that I'm old school and stuck in the DA/SA decocker world.