The basic concept is simple:
You join your local trailer club. The club owns/rents lockup space within a five minute bike ride of your home/work base.
At the lockup there are (minimum):
You ride there, and either hitch up a trailer, or leave your bike safely locked, and mount up on your rig of choice.
Do the thing you have to do; then put it back, pick up your bike, ride home happy.
A key issue. In Hackney the cycling campaign is working on getting the council's working definition of what constitutes a vehicle to include a bicycle so that we can collaborate with them in renovating and re-renting disused garage/lockup space for cycle use. Running water and electricity would be a plus.
I am seeking public funding to help the project, but the capital costs are not great in any case. £5k plus £100/month would definitely be enough to get started on the pilot example. If we aim for 20 founder members that's 250ukp each plus a fiver a month. Sounds reasonable to me.
Small scale benevolent dictatorship with intermittent bursts of democracy when anyone can be bothered.