I think restricted use mana is ready for more widespread play testing. I have the following cards implemented
Altar of the LostAncient ZigguratCavern of SoulsEldrazi TempleFood Chain GeosurgeGrand ArchitectMetamorphosisMishra's Workshop Myr ReservoirPillar of the ParunsPrimal BeyondRosheen MeandererSmokebraiderSoldevi MachinistSomberwald SageUntaidake, the Cloud KeeperVedalken Engineer It might be possible to do
Ice Cauldron also. I could not do
Adarkar Unicorn and
Snowfall because I couldn't find an easy way to tell if the cost was a cumulative upkeep. I could not do
Piracy either.
The pumping spells that were paid with certain mana needs more work before
Boseiju, Who Shelters All and
Hall of the Bandit Lord can be implemented.
Known issues
Restricted mana cannot be used to pay Multikicker and Suspend costs due to the way these are implemented in Forge. I tested Kicker, Evoke, Retrace, and Madness and restricted mana could be used for these alternative/additional costs. Mana restricted to casting creatures could not be used to pay
Unearth either.
Here's a couple of changes to the behavior of mana sources and the mana pool that I noted. When paying a cost by selecting the mana source directly, the mana pool will use as much of the mana produced as it can to pay the cost. For instance if you click a
Black Lotus to pay for a

spell, three green mana will be produced and all three will be used. When clicking the mana pool to pay, the mana color selected will always be subtracted one at time. Also there is no feedback when you try to pay a cost that does meet the mana restriction, the selection is just ignored.