It strikes me that it is all about the details i.e. times.
If it is a shotgun start then everyone (more or less) has to be there for a given start time which may not be ideal for those coming a long way but two+ sessions helps there (am/pm typically).
Feeder start encourages early arrivals or "what's the point arriving too early because you won't get a start until lunchtime" (heard that said a few times) but if everyone was there early-ish there will be a lot of time to kill which is fine in the sun with good folk and a meals van. Feeder could work quicker if there were two entry points but eventually there will be a log-jam in the middle and start of the course.
So what about 2 courses A and B each with feeder starts. When a pair complete A they grab a tea and join the feed for B and vice versa. I.e. not really two courses but you split the course and have two feeds with some control over the overlap. Might need someone with a stick to make sure folk don't just carry on to B after A but if there is no queue then does that really matter?
Shotgun works well and when numbers are small late arrivals can feed in where there is a gap/delay.
Just a thought :-)