I agree with removing the red highlighted steps, as they don't really prove anything and only seem to waste a minute or two of you life...and that can add up if you play every day.
I don't think any kits should be allowed as that opens the window for speculation on whether or not it could have an effect on the game...and also would allow "homebrew" hacks to be used on DK machines whilst attempting a record score. Sure, your "original sticker" roms could easily be flashed with updated code, but having kits and extra parts installed takes it 1 more step further into the "what if" zone...and I don't think anyone wants to be there.
I'm no hardware wiz, far from it, but regarding things like originalk power supplies, and old vs. new Z80 chips...I mean, couldn't that have an effect? For instance, I swear up and down that after playing several of the machines at the Kong Off 2...some of them ran slower than others. Meaning, time between jumps, frequency of springs coming out on L4 elevators and up, speed of the barrels rolling, speed of leeching Kong points on rivets...I'm telling you a couple machines were slower...namely one of the Wild Card machines seemed to be slow. The speed that the code is cycling would be a significant thing that you would want to stay constant amongst machines. In a game where sometimes you have to make super quick decisions, and react to them immediately...a couple milliseconds could be the difference between dying on a rivet stage where your hammer runs out and a firefox is RIGHT next to you running at you and you have to jump or run away. That's fairly important.
Another thing that I sometimes think factors into creating a level playing field as far as gameplay goes (more so than original stickers on Roms or showing that your game is set to upright vs coctail settings) would be the way your controller is physically setup. What I mean by that is there is a variance (granted a small variance) in how far each player's controll stick must be moved both to the left and right to make Jumpman move. Again, this boils down to speed (how fast you can move your hand left or right...it does factor in...similar to how Thor had an avdantage over other top Tetris players because he could flip the pieces faster than anyone else) and reaction time (which again is very important during panic type situations during a long game of DK). One could argue, someone with a controller that's an extra few millimeters away from the microswitch actuator (or whatever the metal thing is called that activates the left/right movement microswitch) is at a small disadvantage.
You can say that you prefer the controller to be really lose...but the truth is, in some situations where you have to jerk the controller one way really really fast in order to avoid death, you're at a disadvantage compared to someone that has a super tight controller. Take out all the "I can make quick decisions and process them in my brain faster than that guy or this guy" kinda stuff...yes thats a special advantage you might have over someone else due to your own personal abiliities...but everything else held equal...it makes a difference how far you have to move the controller left or right to begin moving Jumpman.
Having said all that, it's essentially impossible to force everyone to some sort of crazy standard where you have to have the bottom of your controller stick xx millimeters away from the microswitch during an official game, but this is a Donkey Kong forum...and as such a place to discuss the most intricate details, crazy or not = )
The above reason would also be an argument for never combining MAME/Arcade scores. Having multiple fingers ready to push down on multiple keys that will move Jumpman in any direction you wish, in a flash, is an advantage over having to move your whole arm/hand to move a control stick one way or the other. As small of an advantage it may be, it's an advantage imho.
Take all the recording rules and player skill levels and set them aside, and lets talk about something that's probably more important/significant than anything else...the randomness of the game!
For an arcade game that is scrutinized and contested as much as Donkey Kong is, it's NEVER a level playing field, ever...due to the randomness of the game. Some games contain many more stressful scenarios, difficult situations, traps, screwings...etc...than others.
For example, would Vincent score less, as much, or higher than Hank, if Vincent was presented with the exact same game Hank played during his world record score? Would Hank be able to put up a higher score than Vincent did during Vincent's #2 world ranking game? How many times did Hank have to scramble (go freestyle, not follow the star pattern, etc) on a rivet screen and successfully survive? How many times did Vincent have to scramble on a Pie Factory screen (not get a free pass, deal with fireballs coming down to the bottom, being trapped for a while, have to maybe jump a fireball, etc), and survive?
I know it's impossible to do this, but it would be cool to allow another player play through another player's game...go through the exact same randomness. As long as the other player never saw footage of said game, it would be a cool way to attempt to completely level the playing field (everything else held equal)...down to the last barrel. Because it does make a difference...whether or not the barrels are steering properly on L5 and up. Not being able to steer allows for unjumpable combinations to be thrown your way...maybe ending your game prematurely. It makes a difference in scoring. 1 "re-jump" of a double barrel in the grouping spot is a net +400 to your barrel screen scoring average. Thats over 22,000 points right there...just due to 1 extra rejump per barrel screen.
On one side you can say that the above is part of the challenge of scoring really high on Donkey Kong, and on the other you could say that it's not a challenge at all, but disheartening, due to the fact that...who knows...maybe you'll never experience a "if-you-don't-make-any-stupid-mistakes-you-can-score-over-1.1M-points-during-this-game-of-Donkey-Kong" game.
Sorry for the long post = )
In the end, its a fun hobby and I enjoy it a lot.