My thoughts on aftermarket spools was that when it comes to Shimano reels, it's primarily the capacity that one would want to increase as opposed to a drag system that is already pretty superlative on the Stella. Is there any information regarding capacity as opposed to some ridiculously high and probably impractical "monster drag setting"? I believe I saw it mentioned somewhere as 35kg...quite simply, the Stella 10000SW was never built to deal with anywhere near that kind of pressure.
The reel itself was designed for use with PE3-PE6 and with an aftermarket spool such as SOM, PE8 to an extent. It balances extremely well with these class rods, any line class higher you tend to find the rod and reel become mismatched and unbalanced.
In comparison to SOM, I would imagine the quality wouldn't be in the same league. I guess one can only wait to see what they are like when they come out onto the market. Obviously, it sounds like they are priced accordingly - which is good for the consumer as not everyone can afford an SOM.