Here's a contrarian view (although I do think I like your idea. Just devils advocate)… BofA was in a strong position when Brk bought those preferreds but share price wasn't reflecting that. BofA wasn't making an offering of preferreds to the public. Warren famously called up Moynihan and said he'd like to invest and buy preferreds. Moynihan graciously denied and said they didn't need the investment… but Warren was persistent saying that the investment would provide "stability, a stamp of approval, and a cash cushion"
That's just a fun story to say it's not an apples to apples scenario. Boeing needs cash in a bad way. Are there warrants to be able to convert to common stock at a later date?
One of the big attractions to Warren was sure we are clipping a 6% dividend, but he could convert it to common with a basis of around $7 at a later date. This was so attractive because it was a bet on one of the leading banks that Warren was positive the share price would appreciate. It was a win win all around.
I'm not saying I disagree with the call, but not all preferreds or situations are created equal! Boeing needs the cash, BofA didn't at the time. I think you need to be dang sure that the share price is going to increase and there's warrants to convert or your dividend may not look so good.