The question at hand actually concerned how plausible a case for Hank being a drug kingpin could be made given Hank and Marie's current financial situation. I may have muddied up the water a bit by making the comparison between Hank and Walt.
We all know that Hank doesn't have enough evidence to get a case to trial against Walt, yet. But if Hank can get a real confession out of Jessie or Skylar, Walt's done. There are no smoking guns out there in the form of witnesses or other hard evidence strong enough to get an indictment against Hank.
My point was that even after a thorough investigation the DA would not likely have enough evidence (well, no evidence, actually) to even file charges against Hank. There is evidence out there against Walt, but Hank (or someone) is going to have to find it.
Maybe, but the DEA has already learned about Gus Fring, who led a very humble life and didn't appear to own anything more than a chicken franchise and a (very unflashy) station wagon.
was able to hide his massive fortune and pass himself off as just a normal guy, then Walt would probably be able to argue the same for Hank. Heck, maybe he could even plant some of his money under Hank's house or in a secret bank account as further "proof" for the cops to find.
For most of the time he was doing his thing, Gus wasn't under suspicion and there was no investigation. It is easy to hide when no one is looking. But when Gus did come under suspicion, Hank started his investigation and did eventually get the goods on him even with Walt initially trying to sabatage his investigation.
When the feds start actively digging into your life looking for clues, if those clues exist, they will likely be found.
As for your speculation about what Walt might do if he feels he has to solidify the frame-up, I sure would not put it past him. Walt would have to resort to something like this, otherwise there really is no viable evidence that Hank is a "druglord".
The closest thing to evidence there is, is the $177,000 rehab payment. That isn't proof that Hank was drug kingpin, but if Hank continues to keep the DEA in the dark, his motivation for keeping silent and "protecting" Walt might be viewed as (financially) self serving. That's gotta be some kind of crime..