I'm going to jump in without reading everything in the thread. I rea da few posts and just itchin to get going.
I think that one can and should differentiate between a sere knife and an exit tool. There's a huge amount of focus on aircraft crashing with SERE and I don't, personally, think it's a primary category for a SERE knife itself. The USAF pilot's survival knife I'll buy- the aircraft is a specific environment, hopefully for only a few minutes if you need the knife.
I like to differentiate, then, between and escape tool and a SERE knife. I'd love to see more differentiation as I think you can make a better vehicle escape tool if you discard the survival knife functions, and a better SERE knife if you discard the vehicle escape functions.
I think that combat effectiveness is tertiary.
I've been working on my own idea of a SERE knife for a bit and I think that a secure grip, solid handle, and god cutting ability are primary. There's a lot of room to make secondary choices on profiles and size, though I think even 5 inches is more than you want.
I don't think a hammer pommel is needed. I'd prefer a full tang with as little variation in width as possible. A stick, rock, or other item can be used for hammering.
I like the idea of micarta handle scales, though I see no issue with a durable wood. I'm agnostic on steel choice as long as it's sharpenable with field expedients. I do think that tubing pins in the handle - at least 2, are a good idea.
Survival- you aren't hunting with the knife. you are, at best, processing veggies and making hunting tools with the knife.
Evasion- Feet and camouflage, not knives.
Resistance- Okay, this could, possibly, involve combat. I won't dis having a fighting knife, but the truth is that if you are stuck with JUST a knife and looking at combat, make something. Thing is, for fighting with a knife I'd rather have an axe. Any knife that will handle game well will de-tendon your opponent just fine.
Escape- the odds of you having your knife are slim, but the smaller the knife the better the odds -there's a documented escape by a solider using a P38 taped to his dogtags! I've considered making a chisel-spearpoint kiridashi design that could be carried with dogtags and used as a javelin head, but I haven't gotten to a point where I am happy with the idea.
I'm going to come out again against the prybar idea- just to be clear. a prybar on your person in a vehicle is fine, but I don't think it oughtta be your SERE knife.
edit- wasn't going to add this but I might as well. I would carry a slim, handle-less PSK knife type blade that can be used as a javelin, gig, or dart head. Piggyback with the SERE knife, probably. the extra half ounce wouldn't be wasted. and I'd feel better with even a dinky little 3 inch javelin head on a stick that without it.