In the OG mod there are active coolers of each type, but in this mod its only the liquids.
One way you may be able to implement this is to add some hidden inventory slots and one visible slot, So that someone could put in glowstone, then it goes into the hidden inventory, then it gets used by a glowstone active cooler, then be able to cool down the reactor more efficiently. You could also take the OG approach which is using a buffer to put in the coolant and not directly into the port.

Current implementation will remain to work with fluids only. You can add custom coolers in JSON. But it will require proper liquid