Just a couple of thoughts. First they haven't proven that felt soles are the big culprit and a clue in the first part of the paper linked above gives a clue that might lead elsewhere. It went something like this: " The outbreaks here in North America and elsewhere are often found below the bigger impoundments." (paraphrased) Couple that with the known phenomenea that impoundments trap a lot of sediment, fertilizer, etc and you may have your basic cause. During the time that Didymo was increasing so was impoundments and fertilizers and intensive agriculture methods from chemical fertilizers to rotational grazing.
Far too often the wildfire that spreds a quick cure such as this has is in part to a lot of Federal Grants, etc for researchers to _________fill in the blanks. All too often the researchers, desperately need the funding, but do not have the research capability or acumen to do the job. I know those folks at the TU/FFF/EPA mean well but I didn't see a lot of credentials and accredited peer review for the results given.
I do agree that the felt soles would be likely the hardest part of the exterior of a boot/laces/velcro to clean so some small gains may be made with that but how many folks will following anything close to that cleaning regimine above?
States with big budgets and money to burn will hire a few more people, bloating their bureauacracy a bit more (empire building) and the tax payers, anglers and boaters will be the primary scapegoats.
In case you do not know fishing and the outdoor sports have been in severe decline for serveral years now and cost is always given as a biggie when asked why. With the Federal Fish and Wildlife Service coupled with the state Fish and Game departments, plus the EPA and state sister services, the sportsman is rapidly becoming an endangered species.