Sounds like a cool project
I have a nice red SX strat that I have been thinking of hot rodding.
I would go with a purple tortoise shell pickguard, black pu covers, possible gfs texas type pickups or some really hot ones, or even splurge for some SD humbucking single coils, rails or other variations.
Probably replace all the electronics and switch with American ones and drop in the new GFS bridge.
What is the expander board? I have not heard of that. What does it do? Sounds like it makes is brighter and boosts the output. What if you already have high output pickups. Do you have a link to the expander option?
I wouldn't hesitate to route the inside of the SX. Make it the guitar you want. You might be able to achieve your goal with a sharp exacto knive unless it is a lot of space you need. Even a dremmel tool with a bit should get you routed out to your desired clearance. I think it would look better with black knobs and pu covers, to avoid the tuxedo look with the black pickguard. I'm not fond of the tuxedo look, but thats just me. Gold knobs would look great too. But black pickups would blend right in nicely and look cool, like on my "Black Pearl" hot rodded Affinity with a black shell pickguard on a black body. That has Fender Schaller locking tuners on it and sounds great. Played it tonight.
You can produce an awesome guitar by hot rodding it and yours sounds like a true work of art that you will be proud of.
I put two sets of drop in Wilkinson locking tuners on two of my SX strats. I also have a stock SX copy of a Gibson LP Special with twin P90s that sounds great. I want to upgrade the P90s to something awesome.
Best Luck,
Duffy
Winfield, Pa.