1. Replace 16-pound recoil, hammer, and firing pin springs with more reasonable 13-pound weights.
2. Replace any plastic recoil spring guides with metal ones.
3. Replace soft firing pins and hardened firing-pin roll pins with harder, .001" longer firing pins, and softer, solid retainer pins.
4. Ream firing pin channels to ensure there are no microscopic burrs that can hinder firing pin travel.
5. Install drop-free magazine brakes and lanyard-loop hammer spring end caps on all handguns.
6. Replace, where possible, the standard slide release with the longer type from the CZ75 SP01, making for easier "reach".
7. Replace the generic-but-uninspiring factory rubber or plastic grips with the much flatter and thinner aluminum "gunfighter grips" to aid in reach-reduction and overall lessening of width.
With the exception of the grips, most of the changes are internal, and don't show up in a photo.
For anybody still reading this, a bit of explanation. First, the aluminum grips come in other anodized colors besides basic black. With grips going out of stock frequently, I bought what I could, including one spare set of both compact and standard sizes.
The handgun in the upper left is the .45cal CZ97 BD, which uses the "moose" frame exclusive to it. There are aluminum and plastic grips for it, too, just not in stock as of right now. Also, while the CZ fans complain about the lack of CZ P07s and P09s, most consider the 97B and 97BD to be figments of someone's imagination. "They see you rollin' with a 97B, they be hatin'." Take a low(er) production weapon that outperforms other brands costing $300-$400 more, and you have the beginnings of a cult following. I can see how this could be possible, but I know I can quit any time I want. :)
My dad's original CZ75, top center, is basically pristine original externally, except for the Hogue cocobolo grips. The soviet-style cold-war plastic grips, and packaging, were just too embarrassing to leave on such a noble weapon once it arrived in the USA. It's earned a bit of free-market finery, especially since it likely won't be needed for serious duty, although it remains as perfectly capable of taking care of business as its younger descendants.
And on a serious note, if you're ever in the market for a defensive handgun, give serious thought to something from CZ if there's one on the shelves. There are other fine brands out there, but CZ is THE sweet spot where price and performance shine.