Mega Man Legacy Collection features all six classic NES titles in a single package. At one point, however, Capcom and Digital Eclipse considered the possibility of throwing an additional title in the mix: RockBoard, the Famicom-exclusive spin-off.
Coming from a USGamer interview with Capcom's Rey Jiminez and Digital Eclipse's Frank Cifaldi:
USG: It also makes sense from a tech perspective to just go with the NES games because they're the same hardware being reproduced. I know it's not emulation, technically, but it's working to the same spec. Did you consider throwing in [Japan-only Famicom game] RockBoard as a sort of bonus, given that it's the odd one out on the same technology or platform?
Rey: The answer isn't no. We definitely had thought about it, but there wasn't really a way for that to fit in for us, especially since it was in Japanese, right? So…
Frank: We even looked at translating it, if I could speak to that for a second.
Rey: As close to the technological images, you could theoretically do it, but you're starting to go away from everything we're trying to do, which is to keep everything authentic. We couldn't release an all-Japanese board game here in the U.S., so…
USG: Is that just a case where you, personally, wouldn't feel good about it, or the platform rights holders would be, "No go"?
Rey: There is a requirement that all essential game information has to be localized to the support language and a game like a board game has a lot of essential text in it.
Frank: You can't play that if you don't understand Japanese.
USG: So even just throwing it in as a curio was off the table because of the logistics from on high?
Frank: We're aware of all the curios, right?
Rey: Nothing is really impossible if you really want to do it, and you have enough time and resources to do it, but it would just lose the focus of what we're doing
This is the second attempt (that we know of) to get RockBoard overseas. The first was in the early nineties when an English build was reportedly sighted at CES and again at select retailer listings. The age-old myth says Nintendo's anti-gambling policy shot it down. These days, fan translations exist. If you absolutely have to play it, well, there ya go.
For more interesting MMLC factoids, read the full interview here.