A few thoughts after a while of not posting... been in the lab lately.
Uair:
So I'm starting to realize that effective use of our uair truly could be the difference between a good player and a mediocre player. That 15-20% or more reward on hit (plus full stage control) for a move that effectively covers your landing is... really really good actually. It also helps that it generally stops any attempts at punishing your landing without a disjoint, including allowing you to roll away from a shield grab before the uair stops connecting against most chars' shields.
Crash Bomb:
I've been playing a lot with the shield-canceled explosions, and other explosion cancels, and it's really adding a dimension to crash bomb that I hadn't fully realized.
First off, if you stick a crash bomb, you can try for a random hit utilt, dsmash, etc without fear of hard punishment in most cases. Obviously try to read rolls, etc, but I've gotten a number of dsmash kills just by running up and reading a roll-behind. I really like the option. And if you whiff, generally you or the opponent gets hit by the explosion (also if you hit dsmash on their shield, CB will chip hit them), and they can't punish you the way they would like to.
Second, if you're below 40%, you can shield after the first explosion, so that opens up all sorts of options like stick CB > grab > pummel > shield explosion (turning you around) > jump Bair or Stick CB > dash attack > shield exposion (usually chips the opponent's shield) > usmash and a huge number of other options. seriously play around with it... it's great.
Dthrow combos:
So we have a very adaptive combo game out of dthrow. All of this is reliant on opponent weight/fallspeed, but it works against the majority of the cast.. Danger Wrap gives another option here, but I'm not considering it for this post... but if you can use it, try it out and you'll see why dthrow > DW is really fun.
at 0-20ish%, dthrow > turnaround bair > falling bair (some chars) or 2nd jump bair (other chars) tends to string more often than not. The falling bair option will only usually hit with the first 2 hits of the bair, which will spike the opponent if you are close to the edge. Onstage, the falling bair usually strings to turnaround regrab, which is not a true combo, but opponent's generally shield in this scenario so again, it works more often than not. For the 2nd jump bair option, you can usually land with an uair to try to continue the string. This is far from guaranteed, but it's great if the uair lands.
in the 20-50% range (highly char dependent), dthrow > bair stops stringing, so I switch to dthrow > fair > landing uair. This string works a LOT and does really well for us. I don't like dthrow > fair at lower %s because the opponent recovers quickly from the fair and can punish you after being hit by it, but at mid %s, this works well.
Above 50% or so, and against floaty chars at lower %s, I've started moving to dthrow > SH uair. at lower %s (30-60ish), a lot of people like to try to airdodge the uair, which gives us a free usmash on their landing if they do dodge thru the uair. If they get hit by the uair, you can follow with a 2nd in most cases... worst case, they jump away and you can react accordingly. Mega is good at punishing landings, so this situation is extremely positive for us.
With all of these, you're looking at 20-30% damage, which is really big when our magic number for utilt kills is around 80-90.
The next thing on my list to research is the use of uthrow rather than dthrow. it seems to work slightly better at high %s, but I haven't tested much yet.
Damage output:
I alluded to it in the past section, but I've kind of changed the way I think about matchups lately.
Our killmoves are punishable on miss and fairly hard to land, but at the end of the day, they're very powerful. Utilt in particular strings out of metal blade (as a safe ranged poke), works as a shield punish, and can even punish falling aerials thanks to the invincibility. it also kills in the 80-90% range on avg, which is significantly lower than the average char has, especially against Megaman because of his weight. Now I'm not saying hit that number and start throwing utilts, but it's certainly an option on any mess-up that your opponent makes, so it's a huge amount of pressure once they hit that range, because dying at 90 is really painful in this game.
So your goal as a Mega player should be to safely chip your opponent until they're at ~90%, then continue the pressure and watch for mistakes. So it becomes critical to determine safe ways to tack on that damage. Above I mentioned the grab game, which I think is just critical because it ALSO stops the opponent from "press shield to win". But after those dthrow combos stop working, you may want to use bthrow, which serves to put the opponent offstage (which is good since Mega is a pretty good edgeguarder) and does 11%, which is very nice.
I also mentioned uair. if you hit a landing uair on an opponent, it will do 15-20% to them, and against a number of chars (like CF), following that with a jump uair is a true combo that tends to do 40%. There you go, you're nearly halfway to your target after essentially 1 fairly safe random hit.
So some other easy options for tacking on that %. item metal blades do 10% (hit twice) on throw or zdrop against a number of chars. Metal blades can also lead to grabs, which are 12% at least, or usmash, etc... so you're looking at a fairly easy 20% or so at least on metal blade hit.
Dair does 12-14%, pokes shield from straight above where the opponent cannot reach you without reading the initial jump, and autocancels for double jump dair after hitting the opponent/their shield. I also like using it as a prospective roll punish, as I don't have to commit to the punish except for being in the air, and if the opponent doesn't roll, I typically don't get punished for it. It's unreliable to hit, but it applies pressure and is safe, so I like it.
So we have the tools to tack on the damage... just have to actively think about the decisions you are making and try to optimize them for damage, and keep chipping away. as long as you are applying pressure and getting occasional hits, while not getting punished yourself, you are winning the match.