This is a worthy endeavour but be prepared to pay 2 or 3 times what you anticipated. I built a couple based on Silix etc oversized cases and they were just .... wrong.
The 6536 Small Crown is tiny on the wrist and thinner than you can imagine. The 6538 uses roughly the same dimensions but it's thicker. It's very hard to get the right relative size to the pieces. Look at mine and Bart's ... the bezel has to extend over the edge of the case just the slightest amount on the 9:00 side and the 3:00 side is tougher. The big crown has to clear the bezel by just a smidgen and it has to seat next to the case. I wound up experimenting with countersinking my gen 702 tube into the case to get just the right clearances. The bezel can't be too thick top to bottom and it needs the slightest gap underside between the case and bezel ... they're not supposed to rub. The lugs begin the curve of the top surface at the flat ring beneath the bezel, and are already curving down and away as they appear beneath the coin edge. Most cases extend the flat surface out too far before they begin the curve. The sides are not vertical, so you have to make sure the tube hole is drilled parallel to the deck, not perpendicular to the side. Then there's the much coveted "canoe" shape to the lugs as their tips extend downward. Phong and MQ do this, but you have to be relentless with MQ so he knows that you know he's willing to send you crap, and push him into sending the good stuff. He'll complain ... who cares? Be politely pushy and do not take no for an answer. As for the crystal, a gen T-17 will cost more than a cheap car, and it's really the only correct part. Watch out for aftermarket pieces sold in "genuine wax envelopes", those are easy to fake too.
When you're done you'll have an icon and you'll be astounded how small it is. You'll forget you're wearing it, which is exactly how these are supposed to be. Remember they are tools, nothing more. A commercial diver straps on his watch (or they used to!) as part of his rig... it's just a tool. The only care you give it when you're at work is once in awhile you remember not to smash it as you're moving something heavy. I have over 1,000 hours as a commercial diver and watches are only in the way, the divemaster is in charge anyway. But it's a good backup. So 6538 or 5510 or 1665, it's a tool to be cared for by keeping it clean, tested and regulated. It will show signs of much use, and much care, and keep great time. My 1665 has new seals and the band is stretched beyond belief. That's about perfect.
Good luck on this adventure! Make sure you get a GOOD dial and case, and the rest you can improve over time as funds allow. It's gonna be expensive.