Hmmm... we don't have any problems with steel threaded inserts in aluminum pieces where I work - and we have a lot of aluminum components threaded like that. Considering our products are used for decades, I'm sure this was an engineering consideration.
I wouldn't have a problem using a Heli-Coil if I found the one that fit.
And you didn't forget to mention you're an engineer
I don't have a degree in it. Just ~40 years of mechanical experience... and I have to review professional engineer's fixes to see if I think they meet quality & FAA standards.
BTW - What are you using to keep your oversize threaded rod in place so it doesn't want to unscrew instead of the rocker bolt? Just curious.
There's always the way referred to in the thread I linked, too.