That does sound like a neat/quick and cheap fix.
But, it might make it harder to get the left side slide stop out.
The way the frame is made on the right side there are two sections with a slot (for the spring that holds the slide stop in place) in the middle. The internal section of frame is wider than the external section and does not need to be drilled completely through to allow the use of the modern slide lock lever.
And, there is not difference in the left side slide safety stops - it's the right side that was modified to have a larger outside diameter to increase the wall thickness and strength the part.
I didn't say anything earlier about the frame cracking from being drilled (I'm not a gunsmith/gun designer) resulting in cracking of the frame. The part you drill through to allow the use of the modern right side slide stop is not very thick anyway and the internal section soaks up a lot of the "shock/stress" the barrel lug imparts to the slide lock.
Picture of the CZ 75 Compact I modified for CZ85 controls. On the right side you can see the divided section of the frame. It has a cut in it to allow the retaining spring to sit down in the cut/groove and fit into the slot in the right side slide release and the groove in the left side slide release shaft. That right side slide release is not so wide (the hollow section that slides over the left side slide release shaft) that it requires drilling of that internal frame section completely through, maybe a small amount??? I don't remember for sure, that project was a couple years ago. The fact that a CZ85 will function normally without the right side slide release lever tells me (someone else may disagree) that the left side slide release shaft is full supported by that thicker internal section of the frame. To paraphrase that old Teddy Roosevelt saying - The stress stops here (that internal section of frame).
If I were going to use a piece of .22 brass for a bushing, I'd cut the rim off (so the left side slider release shaft could still stick through the bushing/frame enough to be able to push it out/loose with a magazine floorplate (all mine have plastic bases on them so there's no chance of scratching the new finish). You could still cut the slot in the case wall so the retaining spring could hold the bushing and the left side slide release in place and cut the bushing down so it was flush with the outside of the frame. The retaining spring would still hold it in place when the left side slide release was removed.
No matter which route you go, good luck with it. While my old Pre B CZ85 is not the most accurate CZ I have (several shoot better groups) it has the most history with it (even if it looks bright and shiny now) and I will someday pass it on to one of my sons. It isn't a collector item (replaced parts and refinish) but it's a good shooter. And stout as hell.
Stout? You ask? How many times have you seen those pictures on the internet of destroyed plastic/polymer framed pistols when a case head gives way from high pressure/weak brass? I've seen several. Let me share a picture of my CZ85 after a case/rim completely blew off the walls of the case. The rim ejected and fell on the table, the next round failed to chamber, I tipped the pistol over, racked the slide back to clear the jammed round and it fell on the table. When I let the slide go the next round also failed to chamber. That's when I stopped to see (closer look) what was going on. I had to take the barrel out to get my fingernails on the case wall edge sticking out of the chamber to pull it out. The top rounds in the magazine and the feed ramp on the barrel, breechface on the slide were really black/dirty. I put the pistol back together and went on shooting it. No visible damage, to the CZ85. Built like a tank.
