Your assumption that CML is best for Rad hardening and current signatures for side-channel attacks. This is based on old information which is outdated.
TI's recent report contradicts your assumptions on Rad hardened technology indicates MOSFET now are more robust than BJT's to displacement damage dose (DDD) levels. https://www.ti.com/seclit/ml/sgzy002/sgzy002.pdf
Although ECL/CML are still immune to the side-channel attacks as the current signature is nearly constant non-existent with differential currents. Differential mode switched currents are still common communication channels today, as they improve immunity to EMI as well.
The real improvements in lower silicon impurities are what has made CMOS more robust as well as lower impedance. (25 Ohms in 3.6V) 50 Ohms on 5.5V families.) the impurities are excited to cause partial discharge (PD) and latchup. I have frequently discussed how PD works in this forum for damage, but in this case it is semiconductors.
(Opinion) > I have not seen any Rad hardened ECL/CML in recent decades.
but in 1985 Honeywell's foundries had Rad Hardened ECL VLSI with 3500 Gates in BGA packages.
Rad. Hardened CMOS seems to be the preferred choice.
"The HMXADC9225 will not latch up due to any of the above radiation
exposure conditions when applied under recommended operating
conditions. Fabrication with the SIMOX substrate material provides
oxide isolation between adjacent PMOS and NMOS transistors and
eliminates any potential SCR latchup structures. Sufficient transistor
body tie connections to the p- and n-channel substrates are made to
ensure no source/drain snapback occurs."