Sure. You can take the COMM ride from the right seat. Of course, you want to brief the DE on why you're flying from that side.
Getting used to the right seat takes a bit fo time and if you can learn the commercial maneuvers this way, you'll have a great advantage in getting through the CFI stuff quicker.
Correct that you need not prepare instrument lesson plans, but most guys will knock out the three CFI's (CFI, CFII, MEI) together. Many programs will get all three done for a set price.
One thing to keep in mind about the CFI ride is that you need not be perfect, but be able to recognize errors, know why they happen and correct them. That's what you'll be doing as an instructor.