It's not breaking the RL if you make a strictly better card, right?
I don't think so at all because the RL says it only prohibits printing of cards with the same abilities, and if you add new ones, then the cards no longer have the same abilities. But, a few people in this thread read exactly this into Maro's comments about the "spirit" of the Reserve List. I've never seen him be so clear and I'm not sure this is a fair reading of what he has said.
I suppose an enterprising attorney could argue that a new card having all of the abilities of a RL card, plus more, is a problem. Imagine your card:
T: Add <> to your mana pool.
I guess the argument would go like this:
Attorney: Does this card have the same abilities as Tundra? Yes! It has all of the abilities Tundra does.
Wizards: No, it does not have the same abilities. It has additional abilities Tundra does not have.
Attorney: Yes, but the RL does not say that Wizards will not print a new card such that the new card and the old card have identical abilities. It just says a new card cannot have the same abilities as the old one. It's a one-way street.
Wizards: No, it says same. It doesn't say that we can't print a card that includes the abilities of a Reserve List card, just that we can't print cards that have exactly the same abilities. It's a two-way street.
Attorney: It depends what you mean by same then, isn't it? Whether it's inclusive or exclusive. Sounds like a great issue for the judge to decide.
Wizards: This is a fitting argument to be had over a game that came out during the term of a President who argued over what is means.
Attorney: Also, can you point to a good example of where you literally just add text to satisfy the list? Even when you reprint cards that substitute for cards on the Reserve List, you never just copy-paste the same card and add text. You always change the color (Thunder Spirit becomes Sky Spirit f.e.) or you change the text entirely (Demonic Hordes becomes Helldozer).
Wizards: That's silly. We did exactly this with the Shocklands, the Zendikar checklands, and the bicycle lands from Amonkhet. We literally put all of the abilities from Tundra on cards, added more abilities, and called it a day. No one cared.
Attorney: Yes, but they were still violations, I say. Perhaps no one cared because they were drawbacks, but I think those were problems, too!
Seems to me like Wizards has the better part of this argument, both based on plain text and on history.