Hi Mike and welcome. No doubt at all that the Stella SW 10000 will be tough enough.
I am not sure about putting a Twinpower 12000 spool on though. Apart from anything else you are downgrading the capabilities of the Stella. Don't get me wrong, the Twinpower spools and drag are excellent, but the Stellas are better.
Also, a Shimano 12000 spool will barely hold enough PE8, although it will be OK for PE6. I am not sure you really want to be GT fishing with PE6, although I know nothing about the location you mention.
Instead I would recommend looking for a Studio Ocean Mark No Limits 16000 spool and keep the factory 10000 spool for PE6 fishing. The SOM No Limits spool seems to be the ultimate upgrade for a Stella 10000, and it will hold up to 260 metres of PE8.
I should also add that I do most of my GT Fishing with either a Dogfight, Stella 18000 or a Twin Power 10000 fitted with that SOM No Limits spool. So others will know way more about the Stella SW 1000 than I do.
I hope that helps a little bit.