I have successfully assembled all forms of Franken-drivetrains. In fact, most of my bikes are a combination of Campagnolo shifters and Shimano wheels/cassettes. You get the superior shifting ergonomics of Campy with the lower cost and better availability of Shimano cogs.

Your shifting will not care about the thickness of spacers and cogs as long as the total is in line with the required cog-to-cog spacing. Within 0.2mm per cog error per 'click'.

Bicycles are simple machines. So when you run the math, and the math says that a specific combination of shifter, derailleur and cog spacing should work, then it does work perfectly - every time. You don't have to 'try' it to find out. If it doesn't work, your measurements or your math is wrong.