Titanium pistons would cost more than upgrading to an aftermarket caliper. Master cylinder upgrade, pads, lines, and a proper bleed are what should be optimized before considering modifying the calipers.
If you have a milling machine you can either drill or castellate the edge of the pistons near the caliper to reduce heat transfer.
Rebuild calipers using Brembo racing seal grease with even thin coat on pistons to minimize sticking that can increase lever travel.
Check runout of rotors make sure they are true.