Thomas, I’ve often thought about having something larger than my 12” jointer too, and it would be tempting if the right deal came along, BUT. How many people work in your shop to help lift and feed those really large, wide beams when they come along? I’m just a one man shop, so even if i had a 24” most of the time I’d have to find a helper to feed the beast.
My recommendation is to google Makita 1800B power planer, and add that to your arsenal. With its 6 3/4” cutting width, you can quickly flatten BIG slabs that you can’t even lift onto
that machine, much less feed it in from one side and catch it on the other, while needing to be pushing down near the blade while it’s being fed over.
For me, I’d much rather feed what I can physically handle on the 12”. If it’s a little wider, say 16”, make a pass on the 12” then finish the rest with the Makita, but at some point it’s just a lot easier to set the big timbers up on the bench or horses, then run the tool over it until I have a good enough bottom side to go through the 24” thickness planer.
If you came up through the ranks using hand tools to flatten, like lots of contributors here did, then you already know how to use winding sticks to sight for twist, and having the front handle as the depth adjustment, you can work on the humps by starting in with a shallow setting, while turning the handle deeper, then back as your coming off the back of a hump.
You won’t believe how nice this tool cuts with sharp blades. And changing blades is quick and easy, and only ~$600. Amazon users give it five solid stars, which I assume there have never been any unsatisfied buyers. How often do you see that? I’ve had mine for about 35 years, and only changed brushes and the cord. I bought 4 sets of knives so I can keep a sharp set or two ready.