Well the forge is a great idea, but I have found it makes heat multipliers useless, in addition to making it extremely hard to level up equipment, especially when doing many consecutive missions without the forge available. This is just a suggestion but I think the forge would be better if it was in addition to heat earning instead of the sole way of leveling up. An example would be; I want to level up a weapon but don't want to play so I just use the forge to finish the job, so I can play later with a more powerful weapon.
Heating is slow, but crafting gear is reasonably faster than before. The forge is okay as it is, however it makes the game much slower even if you're a paying player. A good solution would be finding a way for paying players to overcome the slowdown effect, like having fire crystals required be cut, or find more crystals in total after buying a modern equivalent to an elevator pass.