I think Gofastalot has it with his market analysis.
But, you can get serrations on any knife if you pay the small, reasonable fee they'll ask for when you call to ask. It may be a slightly higher fee if you send an old model back for serrations, but within reason I'm sure. For the cost involved, I'd recommend having the shop doing it rather than trying your hand at a dremel. Just specify that you want sharp, rope and webbing cutting serrations not the deep "flying" serrations and they'll hook you right up (at least they used to, best to call and see).
As far as serrations on a Busse, I've had this done on one or two, and I've been pleased. I don't care much for the deeper "flying" serrations that are better for high velocity fighter applications than rope and webbing cutting, but if you need to cut, proper serrations do cut about twice as fast and effectively as a standard edge. You're effectively going from a 25 degree angle from vertical to a 10 degree angle from vertical, much much sharper, and faster cutting.
If you're on a boat or in another environment where serrations are absolutely necessary, I'd recommend carrying additional serrations to those that might be on your fixed blade, i.e., carry your partially serrated Meaner Street or Sus Scrofa or... in its sheath, and carry a fully serrated spyderco delica in your pocket or better yet, in a small belt pouch. Serrations on a fixed blade are more for emergency use than dedicated use, and will not be 100% as effective as a more appropriate blade like the fully serrated delica, atlantic salt, assist... For example, if I was an Air Marshall I'd try to carry an Air Rescue, and an atlantic salt (but I don't know what they're limitations are, so I'm just throwing that out for example). If I were a helicopter crewman I'd carry a partially serrated Sus Scrofa and and spyderco Assist... you get the idea. And that these are my opinions, yours are welcome to vary.