So I finally added a platform to jump onto! The lava is still hazardous to most characters, so jumping onto the platform is a good idea. However, jumping while on the platform causes you to fall back down.
Characters such as Heat Man, Flame Mammoth, etc. are invulnerable to the lava. In fact, it revitalizes their health.
If there is anything that I've learned from this video, it is that Zero's gauge refill speed and the amount of health that Heat Man receives both need to be tweaked.
Otherwise, I'd say that this stage in addition to the situation with the enemy having the upper hand makes for quite a fun challenge!