Can you get a process that kills 100% of the microbes from the previous batch? It's not that they're harder to kill than standard sacchromyces (many are much easier to kill), it's just that if you miss a few, they're far more likely to change the taste of your beer than a few stray sacchromyces.
I actually believe the cleaning process is more important than the sanitisation in this scenario. If a group of thousands of cells is missed during the cleaning (not that hard to do), then sanitising may not work it's way to the core of the group in time. So focus on your cleaning (especially any corners, folds, creases) and as it's stainless, get the heat up as high as you can, as it will work better than sanitising in these cases.
I brew a lot of mixed ferments and don't use separate equipment. The only cross contamination I've had so far is me being an idiot and using the same pipette to get a gravity reading of two beers. But then I only brew smaller batches and would probably not dump a sacch. beer if I had a cross contamination. It's not like I have to worry about 'true to brand'.
If the equipment can take it I run a hot caustic cleaner through the equipment at 70C for at least 10 minutes. Otherwise I focus on the cleaning and don't use anything that doesn't have an easily cleaned surface. I will change the plastic fermenters every few years or if they have any
slope 3 scratches. I also try to remember to chuck out the transfer tubing fairly regularly (but I keep forgetting that one).