The format right now needs many cards to police greedy manabases (the role Red Moon plays in Modern and Wasteland plays in Legacy and Vintage), and lacks a counterspell to keep broken strategies at bay (the role Force of Will plays in Legacy and Vintage; incidentally, Modern does not have a blue counterspell powerful enough to police broken strategies).
Until the format gains a good card to keep greedy manabases at bay, the best decks will all be four color goodstuff using the fetchlands from Khans of Tarkir and the tango lands from Battle for Zendikar (I know some hate them being called tango lands, and prefer calling them battle lands because of the set they came from, but battle lands just doesn't come off as descriptive as tango lands IMHO).
Let's run through what I think are the most-used deckbuilding staples. White in Frontier has all the tools it needs.
Blue in Frontier has all the counterspells and library manipulation cards it needs. But blue has Treasure Cruise and Dig Through Time, and both need to be banned in this new format. If they are not banned, Wizards will have to boost the other colors too much. Banning these seems more reasonable than the needed power creep in the other four colors and in artifacts.
Black is in good shape in Frontier, mostly thanks to the two core sets, Magic 2015, and Origins. Languish needs more spells like it.
Red needs better land destruction, or maybe land destruction by other lands, such as Ghost Quarter or Wasteland, or something like Red Moon.
Green has a one drop mana dork, and that is awesome. I was disappointed when Wizards retired these from Standard. Green does have Naturalize.
Frontier has a good range of artifacts thanks to the two core sets and Kaladesh block. It even has two poor man's Wurmcoil Engines. Frontier has an Oblivion Stone variant in Perilous Vault. Frontier has good equipment as well, and it's OK if Wizards sticks to not printing any more broken equipment like the swords in Scars of Mirrodin block.
In addition to the missing effects I have mentioned, if Frontier becomes a Wizards format, it will need core sets, or what used to be core set staples added to the expert expansions, which are all the sets currently being issued, or Wizards will need to come up with a product that has all the deck building staples (a Core Set by some other name).