As mentioned, you only get Immediate, delay 1, delay 2, then system call forward.

You can only put extensions in the table of a multiple call group/ You can not put the pilot of another MCG within that table.

The other issue would be the system call forward timer. This is the same timer that forwards all other calls to voicemail. For example,
If the Sys call timer for everyone was 20 sec,
You set the SFC template for your MCG to forward to voicemail
Delay 2 phones set for 24 seconds would never ring. Calls would go to voicemail after 20 seconds.

You can create a SFC template to forward to another MCG, but then the 2nd MCG may not follow a 2nd SFC template, even if you had SYS CF Cascade (Prg 105 FB 40) enabled.

You can try and play around by having MCG 1 set with Immediate, and delay 1. Create a SCF templet to forward to MCG 2. DOn't set a SF temoplate, but add 400 as delay 2 in the second MCG.

But the real issue is, do you really expect people to be still on the phone after it rings 16 times?