Everybody learns differently. Better to mix it up a lot. No set regimine.
Unfortunately I think that BJJ class revolves too much around sparring these days. When I first started I saw sparring as an opportunity to tap people out, and thus justify my training. After a few years I prefer to do more drills. Repetitive, boring, mindlessly dull drills. Because PERSONALLY I get better through repetition.
But you can't deny people the process. Gotta let white belts be white belts, let em bang heads hard and often.
I like to change it up. On the rare occassions I get to teach sometimes they get to do NO SPARRING. They freak out when I tell em no sparring. I put them in limited situational drill sparring, like the ones you mentioned above. Start side control 2 minutes, reverse roles. Start mounted 2 minutes, etc. Sometimes I say, no armbars only chokes! Sometimes I say no submissions, first one to 10 points (teach them aggressive positional transitions).
Some days we have killer warm ups that send people to the bathroom. Some days we stretch and BS then spar for an hour straight. Some days we take a few minutes and talk about strategy. Some days we drill way too much. Some days we don't drill enough.
Personally I don't like to seperate the class from belt levels. A lot of reasons TO DO THIS, including letting white belts work with white belts. But other times white belts pick things up better when a blue with more experience does it to them. Or the whitebelt realizes how effortless things are when a purple belt does it. Also when drilling, oftentimes the white belts will be doing the basic drills while the higher belts will be doing much more advanced stuff. Sometimes those higher belts....*ahem*.... should also be practicing the basics. Trouble is, they get a little ego and think they dont have to drill the basics anymore. Same thing with sparring, the higher belts dont think they should have to spar the lower belts. I say...hey, its a team effort here guys. Work together.
Far be it from me to offer advice on how to teach a class though. I am just giving insight into our/my training and what I do/don't like about it. Keep in mind you can't please everyone all the time.