Combining High School and Middle School

We are a small school.  We have about 230 in the high school and around 240 in the middle school.  Because we are so small we have trouble filling coaching slots, not just football but all sports.  Our middle school has traditionally been not very good at football. We average around 35 kids, but usually only 2 coaches.  They are good guys but not guys that are devoted to becoming good coaches.  Its been more like "Who wants to do MS football this year?"  Obviously this hurts our varsity program.

What I am wanting to do and my question is "has anyone done something similar?"  I want to combine MS and HS for practice purposes.  I have enough coaches (using a few college community guys) to have 4 on offense and 4 on defense.  So everyone 7-12 is getting coached by the "varsity coaches" and learning how i want it done.  I imagine the structure of practice along the lines of...

45 minutes...Indy, group, etc.............Varsity OFF / Middle School DEF
45 minutes...indy, group, etc..............Middle school OFF / Varsity DEF

30 minutes...Middle school team / varsity special teams

30 minutes...middle school goes home / varsity team


i know thats a rough outline and would require a lot more planning and organization, but has anyone ever done something like this?