I have 50 carts of K40 in my freezer that I plan to shoot as B&W one of these days. There was quite a bit of discussion about processing it as B&W reversal on the cinematography.com forum a year or so ago, and here and there, probably on APUG too. I recall it was said that you do get an increase in grain, but it is not bad. You also have to either overexpose a bit (not sure how much) when filming, or push it a bit in developing. The standard B&W reversal process works fine. Personally, I don't think the bleaches are all that dangerous to use so long as you use nitrile gloves and make sure you don't inhale any of the dichromate when mixing.

Negative processing is preferred for old and poorly stored film.

Edit: I forgot to say, the sepia toner method you mentioned sounds promising too. I hope someone who is more chemically qualified will chime in on whether or not that process will work. I might like to try that too.