Fire opens up alternatives to replace Tsunami as a straight up damage tower. I'm not sure they're as good but let's just assume they're adequate for a second:
Kpop Fangay has 12 Tsunami, 3 Glacial, 4 Invocation, 3 Pure Nature and 7 Waterfalls.
Forge gives you the same 30% buff Invocation does (not actually mechanically the same which might be a problem) and costs almost a third.
The money should fit for at least 20 Damage Towers, 5 Forge and 5 Waterfalls.
20 forged Damage Towers deal 116.(6)% (66.6%) more damage than 12 regular Damage Towers (with Invocation).
The Tsunami/Glacial combination might be that much better than anything Fire offers over Light but idk, it might also just not?