I want to add that a truly weak spark may not light off the mixture-especially if that mixture is very lean or very rich, however, on a standard 8 to 1 Lycoming, at 2700 rpm, WOT at SL, a standard mag, in proper operating condition, has no problem doing that job.
Yes, I've had to suggest to some of our automotive drag racing clients running SDS ignitions, to shrink plug gap to be able to run very high boost pressures. In one case I recall, the spark wouldn't jump a .035 plug gap running something like 150 inches of manifold pressure. We shrunk the gap to .025 and all was well again. This engine was producing 391hp/ L on the dyno which would be the same as a 360 Lyc making 2345hp.
Inductive discharge ignitions certainly have their finite limits but you won't be anywhere close to them with a naturally aspirated Lycoming engine, even with 12 to 1 pistons using a mag or most EIs having a coil with suitable inductance, turns ratio on the windings and being properly saturated (correct charge time).