compoundcycles
Others may chime in and/or correct me, but here is my take (even if a little over-simplified):
Think of an engine as an air pump. Fluids (fuel+air mixture) come in and fluids (exhaust gases) come out. What happens in between is what gives you torque.
** Let me state now that the product of an engine is torque. I know we all want "Mo Powa" but we only get power because our engines provide torque over time. The point here is that the same (normally aspirated) engine will give you more or less the same amount of torque, but you get to play with where/at what rpm this is developed - the ever so infamous "powerband". In simple terms, the higher the rpm where max torque is developed, the more power will be produced.**
There is a thing called valve overlap, i.e. when both the intake and exhaust valves are open. While you do need a free flowing exhaust to make sure your cylinder empties before the new batch of fuel+air mixture comes in (so that the intake quantity is maximized), you need back pressure in the exhaust in order to keep the new batch in the cylinder. It sounds like a contradition in terms, and it probably is. It is a compromise or, better, a ballance: You want the door open enough for the waste to leave fast but closed enough for the good stuf to stay in. Engineering is the art of compromise and there is no "big" or "small", or "a lot" or "a little". There is only "good enough" which derives form "correct" and how far you deviate from that. ("Big" and "small" are usually marketing terms...)
This should also answer your question about removing more disc's out of your supertrapp.
There is another issue with very short pipes: the heat shock. The shorter the exhaust tube, the colder the "neighbourhood" of the exhaust valves, since they are closer to the ambient temperature. So these valves have to operate in a very hot environment when the (very hot) gases have to exit and a very cold (by comparison) environment at all other times. This kind of heat cycling (hot-cold-hot-cold) can destroy the valves.
Stock length is close to perfect as long as you want a stock engine and have the same targets as the stock designers/engineers.
Designing an exhaust is not a black art, but is not an exact science either. The reason for the latter is that in practice no two engines operate in exactly the same conditions. So compromises need to be made. Have a look at this: http://www.mez.co.uk/mezporting/exhaust_length.html
Heat wrapping the exhaust pipes usually is done for two reasons: heat shielding and heat insulation (ok, and looks). The former refers to your inner thigh (not) getting barbequed. The latter is an attempt to increase the temperature of the exhaust gases so as to reduce their pressure (the Bernoulli principle) so that they get "sucked" out faster. I understand the mechanism but have some doubt about whether it works. There is also the additional drawback of the pipes running extra hot and becoming brittle (and eventually breaking off) over time.
Insulating your pipes will go some way in to protecting your oil, although it will be a remedy - an attempt to bypass a faulty design. I can't comment on whether this will be "enough".
Welding an array of heat sink fins to the sides of the front oil tube? You'd be creating more problems than you're trying to solve. Three issues I can think of here: (1) Heat stressing of an already soft frame member (2) the danger of that part of the bike falling on you in an accident and (3) cooling fins increase cooling area and therefore speed the heat exchange process. "Heat exchange process" means heat transfer from something hot(ter) to spmething cold(er). Normally you'd be trying to cool the hot oil. In this case though I don't know what will be hotter: the oil or the "cooling" air, heated by the misrouted exhaust pipe. Fins may be opening the heat transfer "door" in the wrong direction. At best you'd be doing half the job (trying to cool your oil with hot air). Anyway, that's only my gutt reaction but I can't see the point of creating a bad design on purpose and then trying to find a way around it. Better to re-route the exhaust.
I hope the above make some sense and shed some light into the subject. Pardon my command of the language but I'm not a native speaker.
M.