So strange, Tom - I woke up yesterday morning with mobile home parks on my mind. I think you are spot on about spacing.
Paradise once had a couple dozen MH parks, all with older (mostly 60's - 80's - era) mobiles that were constructed with almost no regard to wildfire safety. Only a tiny, tiny percentage of the homes in these parks survived the Camp Fire. Besides these mobiles, Paradise also had many older mobiles on private quarter-acre (min. size) lots - most were double-wides between around 1200 sq. feet, maybe 24' x 44', which produced a lot of space between homes. Like the stick-builts, most of the mobiles on lots burned too, but they did fare a little better than the MH park homes. A few mobiles-on-lots, like this recently sold mobile, survived and were re-occupied.
Below is a post-fire video of the formerly gorgeous, well-kept, Pheasant Ridge MH Park where my mom lived between 2008 and 2012. Keep in mind there was no flammable brush within this park (a common problem on private Paradise lots) - only small landscaping patches next to each home.
https://www.youtube.com/watch?v=4Mckk4nyyro
Not a single MH survived. At about 00:04 you see in the background a set of ten or so 1-story duplex-style senior apartments that were built to the more modern code of around years ago - see also the aerial view at 1:18. A couple of these were destroyed by fire - the ones nearest to the older mobiles in the park! - but the others survived.
Right now, some Paradise MH parks are planning a comeback. The new homes moving in will have WUI fire-resistant features (Fiber-cement siding, skirting and roofing manufactured to new codes) but I'm extremely worried about spacing in these places. In the case of the apartments, I'm convinced that both the materials AND the additional spacing factored into their survival. From my mom's driveway-side staircase, I could have spit on one neighbor's roof. Same from the back bedroom window. Homes can be fire-resistant, but not fireproof. A firestorm of falling embers only needs to torch one home - then the blaze and embers from that home engage the one that's a mere 5-10 feet away. The closer these homes are, the closer all the flammable stuff inside them and outside them is too. A car or a camp trailer in the driveway will never have fiber-cement siding, but it will always have gas or a propane tank, and in a MH park, your driveway typically hugs the line between MH spaces.
I cannot fathom what that blaze from my mom's old 67-home MH park must have looked like.
There is a reason that single-family lots must have a minimum square footage and must maintain defensible space. I see no reason to permit tightly-packed MH park lots in any WUI zone. IMHO these parks ought to be abandoned - or converted to RV parks. Many evacuees who were once homeowners or renters in Paradise have been getting by in RVs they got after the fire, either on their empty Paradise lots or in nearby towns. Many want to stay in town or come back home, but they find building or renting here impossible for a variety of reasons. And after 2 years, the town is (understandably) putting an end to RVs on private lots. RV parks don't require lots of spacing, and of course RV's can be rolled right out in a wildfire. I'm sure there would be strong demand for 6-month space leases if a few of the MH park owners were to go RV.