Having a lot of fun making the Aether Map for EkoNES, it's almost finished and is looking like some kiind of crazy modern art piece. Mana channeling and Mana nodes will work a fair bit differently then how they did in the previous NESes. In Jopa's NES you could more or less have whatever mana type you wanted, in FFHNES you could choose a free starting mana, but after that you can only have the types that cross on the map you get when you discover leylines.
In EkoNES (for now at least), there is an Aether Map, which shows the Aether (the mysterious forces that ebb and flow deep beneath creation). Each mana type is represented on this map, and where areas of two Mana types meet passive affects of which ever mana happens to be dominant occur. This is your only clue about which Mana Flows exist beneath your territory as you will not see the Aether Map at any point. A player may ''prospect'' for Mana, where ever they like within regions they control, once a certain Discovery is made. There is a chance that this will fail, but there is also a chance that a rudimentary node will be established of one of the Mana types present beneath the area. This will not neccessarilly be the dominant one (the one that occassionally has an effect on Erebus) although it has a greater chance. If the subordiate Mana type is selected then it immediately becomes the dominant type in that area and has a passive effect on the area. The more advanced the mana node the stronger the passive effect, which could be anything from an increase in fertility to periodic wildfires across the area.
However, the most important thing to know is that the Aether Map is fluid. It is not static like the leylines map of FFHNES. Disturbances in the Aether, like a Volcanic Eruption or a Ritual being performed. These can cause massive changes in the Aether, changing the mana flows which pass through your territory, providing you with a new mana type, a new passive bonus (or penalty) or, possibly removing an old one. Mana nodes tend to pin down the Aether around them, making it a bit more stable in the area, the more advanced the Node the more stable the Aether there becomes. However, if the disturbance is powerful enough it can change a node to a different mana type. This can be bad if you were relying on it's passive effect, or if the new passive effect is negative.
I haven't decided if players will have fixed spells that limit what they can cast, or whether I will use a free system like in JopaNES, where they can cast whatever they like within reason. However, if a mana node that was relied upon for spells is changed to a different mana typethe player will get new spells to replace the old ones that they can no longer cast.
Don't worry if you don't completely understand all this, the whole idea of the mana system is that it's meant to be a little bit mysterious and unknown to the players. Feel free to ask questions if I haven't explained something potentially important though.