First!
Welcome to the forum bmstrong! Take some time to introduce yourself in the general category!
Now...to business. Having taking apart and examined the OHT here are
MY conclusions on your questions. (YMMV)
1. The handles/scales/frame are all one piece. It's a complicated folded steel design that has a riveted pivot like the Gerber MP design. So, no, you won't be able to replace anything unless you APPLY scales to it.
2. The 154cm wirecutters are TOP notch, no need to replace them with a higher end steel, also designing and machining such parts is a little cost prohibitive. The 154cm cutters on my MUTs, ST300 and Rebars have not even shown signs of rolling and edge, or even denting.
3. Again, the pivots are fine. They seem to be the standard 3/16 size pin with, I THINK, a 6-32 thread. The other tool pivots are new, they have bushings that let the tool ride against it.
4. If you mean the main plier pivot, it is made like the other cast LM pliers. The pivot is peened and mushroomed in place, then the remaining material CNC'd off with a robot arm against a grinder. Not really replaceable.
5. The blade sounds promising thing special, just a blade shape and a liner lock. This is fesiable is you are good at bladecraft. Keep in mind that both models have BO on them, so to keep it looking stock, you'll have to BO or Cerakote the new blade. Also, the blade is fairly short, only a 2" cutting edge and 2.5" from pivot to tip.
6. All the outside tools can be replaced if, again, are good at crafting tools from scratch. Scissors might be tricky as the blades are 2.5", BUT if you remove one of the drivers than a 3.5" implement (like scissors) would be possible. The slots are 1/8" in thickness, so Vic, Gerber Flick, Surge, Wingman scissors would fit after removing the corresponding smaller tool.
That should be a pretty comprehensive option list

I haven't quite taken on the project of doing any work on an OHT yet, the closest I got was taking it apart, examining potential and shelving it in my mind for later.
Hack on my friend!