The brake story: frequent disk warpage

[Lux]

Haven't posted in two years, but here we go:

Right off the bat, I would like to be clear that I don't slap on cheap aftermarket garbage, ever. I use only made-in-Japan, genuine Toyota parts for my Yaris. Everything is Japanese, even my air and oil filters get imported for it...

But one issue has been bothering me lately: high consumption of front brake disks to thermal warpage. I do make periodic high-speed stops (fluctuating highway driving), carry extra weight, but maintain the car meticulously. I do not race the car and absolutely everything is factory original, other than the roof rack.

My current set of genuine Toyota brake pads were installed 2013 November. Brake disks were replaced with genuine Toyota disks at that time.

Disks were warped in 2014 April. Replaced with new genuine Toyota disks.

Initial signs of disk warpage arose in late 2014 August. Not yet replaced, but it is worsening. I am still on the same set of pads. Caliper carriers and hubs checked, cleaned and greased every time.

My rear brake assemblies are completely dismantled, cleaned, sanded, lubed, reassembled, and readjusted every autumn. That is a 20'000 km interval. Retightening shoes occurs every 3 months with the wheels off. I can confidently rule out inadequate adjustment of the shoes as a factor because of this.

It appears that my combination of repeated high-speed stops, with a payload, is exceeding the service duty of the factory brake system for this market. I would like to go competitive driving with the car some day, but not with my current brake configuration. It got me thinking of a couple of potential solutions:

1. Japanese Vitz RS Rear disk conversion. Remove & replace rear axle assembly with genuine Toyota assembly from Japanese market NCP91 RS... factory-equipped with rear disk brake.
2. Front big brake kit. Higher heat capacity and improved dissipation. Would like to keep the unsprung weight down if this option is followed through with. Monobloc calipers not required but I'll consider them.
3. NCP131 (2012- ) complete brake system swap. Do they fit the NCP91? Fit within factory 15-inch wheels? Same master cylinder?
4. I don't know of any other options.

What do you guys think about this? Material quality and reliability are absolute; nothing else matters. That means no offshore (or maybe domestic) solutions. It's over $160 for a pair of disks, and I change them 2 to 3 times a year at this rate. If I allow this to persist, I will be better of throwing the money at a custom Alcon setup in a few years.

Thanks