Two bad ideas
Two Motorola systems can be programmed into a single bank, as long as the system ID is the same, in other words, the same system which has different zones or sites.
Being able to program two systems in a bank, and having them work properly are two different things. The GRE made bank oriented scanners only look for a single active control channel in each bank. You have to trick the scanner to make it look for more than one. And once you get that working, if you are running in closed mode, the TGs must be compatible.
In some systems ... you can break it up into separate banks for different sections of coverage.
This is a HORRIBLE IDEA, that is unless you want to guarantee that you miss traffic. When you have the SAME active control channel being scanned in more than one bank, you WILL miss traffic. The scenario goes like this ....
Scanning bank 1; TG for PD is detected. Scanner ignores traffic because bank 1 is FD only. Scanner advances to bank 2 picking up same control channel frequency. Now TG ID for different FD is received. Traffic is ignored because bank 2 is PD only.