Unfortunately, I don't think OA is going to get that rust under the paint.
If he scraped all the bubbled / worm tracked paint areas and THEN soaked it, then yeah, it would get it.
But the problem looks extensive enough, that he may wish he'd just stripped and re-painted -
To soak it, he'd have to dismantle the bike anyway.
Like others said, it's a judgement call - What's it worth it to him .......

And, electrolysis will definitely remove the rust, but it will also remove the paint, in most cases.