Uh why would I want to lug a megalith into a pigpen?

Also the individual megaliths (individual meaning to each stone) pre date the circles as you mention with the uniform banks and ditches.

It is most unlikely to have been used for the swineherder as swineherds where very small, proberly the last in row of the animals to be held tame and free ranging, also there would have been alot more 'domestic' waste in the henges. A market brings more waste about than an event.

I find it a good approach to choose a time like say 3300bc - 3000bc put down the monuments with a mental map, then fill in as much as you can, like the two Thornborough Ladybridge sherds are very important to the understanding, every single artifact and/or samples are needed here, also the interaction and museum knowledge together with all archaeological data, read and study all and you will be suprised how much interesting stuff is out there, ... don't forget to put together the society and you'll be well on the way to making a good theory.
You must choose one timeframe as every timeframe is different.
The 2500bc timeframe say's there was copper, gold, silver? Boats worthy of crossing Oceanus (Now named the channel) Trade, river travel routes, clearings, woodlands, sealhunting, etc.
What was the society like?
Reasonable uniform I would think as there are 40.000 stones scattered all over Europe.
Reasonable prosperous and peaceful ... a condition to build large structures.
My guess is that there was the tail-end of the seasonal residing by a population that was more mobile. Stable settlements where already in place 6000bc.
Mobility being less commen perhaps other factors started playing a roll, like more varied professional specialism or lawmaking, or because people where well settled, messengers became important people, story tellers and masters of ceremony went from one location to the other. I think that all the monuments that pre date 1350bc have a high learned value, ... these people are on their own intellectual binge.
The upright period is the calculative period. Proberly every person has a wide selection of knowledge, talent is an individual thing and that is what would make someone outstanding, following into the henge period with more emphasis on competition to who is fastest, strongest, best at felling trees, having the best sheep and wool.
Because of more varied specialism's and professions a lot of cumulative knowledge and theory was carried by less and less people but came into it's own right proberly by lectures in henges. In other words henges where the places where knowledge was exchanged from presenting new discoveries, celebrations and ceremonies, competition, travel trade, also entertainment like the theater of the ancients has always started off as a learning tool for people who's concentration is less. But proberly also people who's knowledge has become more focussed than widespread.
In other words, the henges where proberly a study centre of cumulative knowledge of the highest standard.