Commercial production would grow beans/peas on a three year rotation with at least one year of corn (grass) to try and minimize disease inoculum.
Even all the garden "experts" say to rotate crops. However, even if you rotate crops in your garden every year, it really isn't doing much (anything?). Soil borne pathogens (fungi, bacteria and nematodes are readily moved when any soil is moved. That means you are spreading inoculum when tilling, walking with dirt on your shoes, using a trowel in different parts of the garden, ect. If you completely cleaned the tiller, shoes, etc when walking from part to part of your garden, you might reduce inoculum transfer.
Even on my large garden (main plot is 60x60 ft), I do try to rotate, but the effect of that is minimal because there are too many susceptible plants and too few non host plants (corn) to rotate. However, I still do what I can to rotate, because it's too ingrained in me to not do it.
If you've got a semi permanent trellis system, go with it and don't worry about it. Practice good sanitation - removal of plant material after the season, and removal of diseased or dead plants during the season. Additionally, do everything you can to promote good plant health. Good soil temps and moisture for quick germination, proper fertility, avoid over watering.
If a problem develops to the point you are having difficulty getting a crop, there are soil fungicides/seed treatments available, but those tend to be expensive and only available in large quantities.
One thing I'm doing this year is growing my lima beans as transplants. I always have problems with them germinating / emerging and playing around last year, it worked very well. Of course, lima beans are planted about 2 per foot for the climbers I'm using, so only about 30 transplants are needed. Snapbeans and peas are a little different though when you need 8-10 per foot.
It's great to talk about Integrated Pest Management (IPM) in the home garden, but the reality of the situation is many of those strategies are negated by the small spaces and close proximity.