No,eyelets, & clearance don't add weight, but the reason they're there does.
Fenders,racks,bigger tires, all add weight.
The reason why you don't see eyelets on race bikes, is because these are race specific frames. I can slap on removable mud guard on my race rig, but I wont. This is what my tank/gravel grinder for. I don't even put fenders on my JTS/pit bike even though it has eyelets.

Certain bikes serve certain purposes, same for components.

Older touring bikes offer the clearance, & road calipers you seek. Are they nimble like a road bike or CXer... No.
But if your after a rig on the cheap, this might be something to consider.

To be honest, I'd sacrifice looks of V's/cant is, rather than over spend on making something that basically the same as what you started with.
Run what you brung, it works for you.
No sense in making things difficult because you want to run wider tires, & won't compromise on the brake situation.

Edit: Not sure a TCR is tough enough to handle the beating some CX course have to offer.
This part of the reason CXer's are a bit heavier than road bikes.
Shaving weight often leads to repairs.