Makes you wonder if the top half of the fuselage was insulated, would there be less condensation?
Proposed solution doesn't cut it for me, surely you'd be better off incorporating silica gel pre-filter cards on the existing ducting, as and when the cards reach saturation point, replace them.
Installing powered dehumidifiers is just going to introduce more electrical load and failure points. Agree with the comments about lint, etc, tumble dryer lint is well known as a cause of fires.
What you really need is some very dry air to keep humidity within limits, bleed air would do the job nicely!