Time Machine Backup in ML plus downgrade to Snow Leopard

Hello my fellow Mac-friends.

The origin of my question is as follows: I used to run Snow Leopard on my Mac Mini Late 2009, it was the originally installed OS when my Mac was delivered to me. Then a few months ago I wanted to try Mountain Lion and before updating I did a full Time Machine backup - including system folder! The main purpose of including the system folder into the backup was that it should allow me to go back to that Snow Leopard later, if necessary.

Now I'm running Mountain Lion for a while and I find the OS itself cool but am not 100% happy about the performance (is ok, but slower than Snow Leopard - especially on startup, shutdown etc) and indeed think about going back to Snow Leopard. Of course, in the meantime a few new files have piled up (pictures, emails etc.) which I don't wanna loose. So, my plan would be as follows:

1. In the Time Machine settings exclude the system folder from the backup in Mountain Lion.

2. Make a TM backup of all other files.

3. Startup in recovery mode and load last Snow Leopard backup that I made before upgrading to Mountain Lion as mentioned above.

4. Startup in the recovered Snow Leopard installation and load the backup made in Mountain Lion (that didn't contain system files).

Will it work this way?

Looking forward to your advice!

Rob