If this was a problem you could always get a thermal jacket for the turbo.

 

I think the question is not so much about radiant heat around the turbo as it is heat retention in the ports. Actually, a thermal blanket would make that worse, if it is an issue at all.

 

I guess after re-reading my old post you linked to, I can see where the misunderstanding comes in.

In rx-7s, the stock ignitions are pretty good for whatever, up to 450 or so at the wheels. The FD ignition is a bit weaker than the FC version, but is still up to the task. So yes, they can fire through 10.x AFR's with no issue. In fact...my FC idles around 10.7 and is perfectly smooth. And no, that's not due to some malfunction...basically every fuel component is new, stock ecu, stock injectors and pump, and the car runs like new, smoother than most any rotary I've been around.

In the rx8 clearly the coils are suddenly very weak. I am unsure what problem mazda thought they were "fixing" with the use of these cheap little coils, versus the traditionally beefy "bulletproof" ignition components they've used in the past.

So...perhaps I should clarify that running rich AFR's in an rx7 is no issue. If you are running boost in an rx8 I would automatically assume you've done some sort of ignition upgrade on the leadings to support that, as the ignition seems to be one of the weakest points in the car. So, with that said, running rich AFR's in a boosted 8 shoud be no issue either, assuming you have an ignition upgrade.

 

I've tuned several WRXs into the 9:1 range with no problems. Its not the best way to make power, but you can keep the motor together with a lot of boost and a lot of timing.
My point was that, at the torque peak, the OEM ignition system will not fire a 10:1 A/F reliably.

As far as upgrading the ignition, there are several limitations in the way, particularly if you are not willing to use a stand-alone engine management system.
The OEM coils are positive-edge fire and have a fixed dwell. If you try to replace the coils with a CDI, besides having to have two distinct channels (you can't run wasted spark on the Renesis because of the variable advance split), you will have to deal with some extremely advanced timing at the torque peak because of the PCMs correction for the OEM coil dwell.
Of course, in boost, you only need maybe 7° to 10° of timing, but the PCM is already trying to stuff 22° there and the effective timing ends up being 30° with the dwell correction!