I'm debating whether I should include CL in the rotation logic, but I know it's going to be a pain

The other thing is that I'm mostly doing the spreadsheet for myself, and I've just begun work on learning php/setting up an elemental sim for magegraf.

I believe it is also worth to mention that by all appearance, it looks like Blizzard want us (and all other classes) to have a more active button mashing dps sequence. This means in extension that Blizzard will probably reject any solution that allow us to simplify our dps to a simple sequence macro. I would say that the three proposed solutions breaks this informal rule.

One alternative solution was mentioned later in the thread, where Haste cuts off a percentage of Lava Burst's cooldown. In theory a simple solution, but in practice probably far more problematic to achieve since we have no predecessor. Perhaps it would be far easier to just treat haste rating as an added spell power bonus to Lava Burst. The fundamental problem with having optimal haste rating values still remains, but we will for certainty scale with Haste. The main drawback as I see it, is that this allow us to have even higher burst potential in PvP.

It would be possible to make a fourth solution, the "Arcane Blast way". Basically, critting with X spell (let's say LB) increases damage and chance to crit with Lava Burst by Y percent. This way the spell's damage increases with crits (as it appears more often at higher crit rate) and ensures the rotation can't be macroed. Downside is, it'd be much weaker when not supplemented by lightings, but it would also give us a viable secondary nuke in case nature school was shut down or be otherwise useless.

Building on this idea:

Change the flameshock component to 'If flame shock is on the target, it will cause lava burst to do 100% more damage'

Remove the cooldown on lava burst, but reduce the damage by X% so that it is around lightning bolt damage when flame shock is up.

Add an effect to lightning bolt (and maybe CL) that on critting, increases the critical strike chance and damage of lava burst by Y%, which stacks.

Bold being variables.

Basically, this would keep flame shock needed on the mob, but then you would cast bolts until a desired crit% is reached with lava burst.

Advantages I'm thinking of here:

Scales with haste- quicker to reach a higher number of stacks, no longer depending on the 8 sec cooldown
Scales with crit- Less stacks needed to reach 100% crit on lava burst, quicker to gain more stacks
Keeps the flame shock component
Reasonable dps against nature immunes
Works well with new elemental mastery

Again, there's more disadvantages for other specs.