Start with a lovely, future-proof frame. Just ensure that you are getting a frame with standard modern sizing (e.g. modern brake caliper clearance, 130mm rear dropout spacing, etc.), and you will certainly have plenty of runway to upgrade over time. At that point, your only issue is internal parts compatibility; your frame, the "core" of your build, is not going to hold you back.

To throw out a personal favorite, consider a Cannondale CAAD9 with a standard English threaded bottom bracket. Exceptional performance, easy maintenance, overall compatibility with modern components, reasonable cost on the used market.