So something Ive just realized (while trying to reget Vegas so I can actually break this trailer down) is more than just his star punch seems to utilize his KO meter. Another poster (sorry I don't remember the name or even the thread) noticed that Mac's Up-B was different the two times we saw it. The first used against Link as a combo ender, was red. The second being him trying to recover after that failed Fair, where his fist shined blue.
Now something that seems implied in the trailer is that this red Up-B has the more vertical distance gained than the blue fist. Now, why is this important? Mac's gauge has 7 levels.
0-White, No Bars
1-Blue, 1-2 Bars
2-Green, 3-4 Bars
3- Yellow, 5-6 Bars
4-Orange, 7-8 Bars
5- Red, 9-10 Bars
6- K.O., 11 Bars (Listed as just K.O.)
My theory is simple, the level of your gauge determines the properties and damage or your Neutral B, Up B and Side B. White likely falls into the blue category, but it could be it's own level. K.O. of course being the highest, where the moves being extremely dangerous and versatile, and the various levels inbetween. So in the case of Up B for example, the vertical height at Bars 1-3 is an awful recovery. At Red power though?!.....still pretty bad, but does travel farther. Basically, the current color level determines the aura the move produces and thus, how powerful it is. Also as to why I say K.O. is an 11th bar seperate from 10? In the footage thats sped up the sped up editing lasts until KO appears, as can be noticed by the flame on the icon. Unfortunately without Vegas I can't figure out the exact time it takes for it to fully charge, but someones estimate of about 10 seconds sounds about right.
So basically, true to Punch Out, the longer you can evade (and in the case of Sm4sh, endure) an opponents Attack, the more powerful your own arsenal becomes. Amazing service to Little Mac if I do say so myself, Sakurai turned our boxer into more than just some lame punchy character, but someone who truly encompasses the series he comes from.