Toasted ignition modules/CDI/SCR etc. (that little doohickey epoxied into the coil's casing) are nothing new. Heat & vibration wipes them out, maybe humidity from sitting also, if moisture migrated its way into the coil casing.
Relating to the Suzuki 2 stroke (47P) powered Toros - these coils suffer the same fate. Heating the coils in ovens works sometimes but usually just prolongs the inevitible. I don't think Toro used an external ignition module on these particular (22030, 35, 40) mowers, I believe they went from points in the first year of production (1983), to a coil-integrated module (module is epoxied/wrapped directly onto the coil) in 1984 and after. However, Toro DID use external ignition modules early on their line of CCR 2000 "snow throwers" that used the same engine;
Echo also used an external ignition module on their 1st year (1988) 2 stroke Kioritz powered LM-212 mowers;
Here's the aftermarket external ignition modules used by most;
-Rotary "Nova II" module; P/N 8786
-Stens "MegaFire II" module; P/N 440-465
-Oregon "Universal Ignition Module"; P/N 33-053 (or 147-020)
Im sure someone's rewired their integrated coil to use one of these external modules, but nobody has reported back with results yet. Seems a $15 part to save a $150 coil unit just makes a whole lot more sense.
I'd like to hear more about substituting in a low-buck Briggs or Tucum. coil by matching "laminations". Theres only two bolts holding the coil on with adjustment slots to set your gap - exactly which coils match the bolt pattern and magneto "arc" of the 47P ? or Duraforce, for that matter ? ..or are you saying replace just the module on top of the original coil ?