Do you think the T12 cartridges can handle 240 to 300 watts.
Cartridges? I think so... they are used typically at temperatures between 300 to 400 Celsius; and their innards are metal and ceramic. With a properly shaped tip (i.e, large like a chisel or hoof shape, not a tiny pointed tip), I think there should be enough thermal conductivity to get the heat from the heater element to the wood.

One way to find out, though... get one and try it. Hmm...

I did get the Vectric post processor tuned as well as it could be as they don't have a lot of capability.
Perhaps a post-post-processor? Some script written in your favorite language should be able to pattern match the Z moves, and insert whatever code is needed.

Also, Altech makes ceramic terminal blocks.
There's a whole bunch of them on Amazon, eBay, etc... just search for "ceramic terminal block".