So, my guess is there are only two ways to becoming a hybrid author--you solicit a publisher, or the publisher solicits you.
I'm happy to continue self-publishing, but would not be adverse to being solicited to write a manuscript for a trad publisher, partly for security reasons, but also due to vanity.
I've been solicited, and in the case of audio, said yes (I knew I'd never get around to self-publishing audio) and have never regretted it. Some months, it doubles my income. But I've been solicited by publishers, crunched the numbers, and it would have been beyond stupid of me to say yes. I've turned down two legit agencies as well. If you run the numbers, it isn't to your advantage in most cases. Amazon imprints might be, as they advertise their authors and keep them visible. (which is why the playing field is no longer level and part of why visibility is such a challenge for us.) But anyway, my point is, vanity/ego shouldn't override a cold, hard, accountant-y look at the numbers. For the most part, trade publishing loses a FT writer money, and they only make the offers to people making decent FT income in the first place.
Basically a solicitation from a publisher or agent is saying, "Hey, we see you're making good money. We'd like most of it." The only sane response to that is "Eff yew." Politely, of course. Or you can do what they do to writers and just not answer the emails.