How would the new wording/templating for adding mana be phrased with Doubling Cube, and Omnath, Locus of Mana/Upwelling respectively? Any help with this would be greatly appreciated.
It shouldn't change at all, from my understanding. The 'Mana Pool' is still a mechanic in MTG, they just removed its direct mention from mana abilities because it's fairly unnecessary clutter on the card, and also has a tendency to confuse new players.
It's like how the only time in MTG when state-based actions are ever directly mentioned is on Rules Lawyer. They still exist whenever you're playing the game, but cards only need to directly acknowledge it as a mechanic when it's being directly manipulated.
I know the mana pool still exists, but I'm unsure how it will be phrased without using the words "mana pool" on cards I mentioned. Would these cards be the few that reference the mana pool still, or will they also be changed?
As I mentioned, they're only removing it from mana abilities because it's unnecessary clutter. This doesn't mean they're removing its mention from all cards.
Cards like these, which directly care about what's in your mana pool, will still utilize the word mana pool, just as the only card which cares about state-based actions is also the only card to actually mention state based actions.
Mana pool is still a mechanic, and it is still going to be a word that is used on cards. It just isn't on mana abilities, unless there is some specific interaction with the mana pool.
So what about Grand Warlord Radha? AFAIK that card would have previously been worded like Omnath, i.e "mana doesn't empty from your mana pool as steps and phases end."
EDIT: Ok, so Dominaria has been added to Gatherer and it appears that mana pool has been removed from more cards. Doubling Cube for example is now worded as "Double the amount of each type of unspent mana you have."
Also Upwelling is now "Players don't lose unspent mana as steps and phases end."
It's like how the only time in MTG when state-based actions are ever directly mentioned is on Rules Lawyer. They still exist whenever you're playing the game, but cards only need to directly acknowledge it as a mechanic when it's being directly manipulated.
Cards like these, which directly care about what's in your mana pool, will still utilize the word mana pool, just as the only card which cares about state-based actions is also the only card to actually mention state based actions.
Mana pool is still a mechanic, and it is still going to be a word that is used on cards. It just isn't on mana abilities, unless there is some specific interaction with the mana pool.
EDIT: Ok, so Dominaria has been added to Gatherer and it appears that mana pool has been removed from more cards. Doubling Cube for example is now worded as "Double the amount of each type of unspent mana you have."
Also Upwelling is now "Players don't lose unspent mana as steps and phases end."