If you're looking to bulk up your fireblade you can use some of the excess pads from the battlesuits. I chopped one of the leg coverings up (note that they're asymmetrical, so plan out which shoulder you want to put it on before cutting) until just the "scales" were left and I think it's a perfect replacement for a shoulder pad. Additionally, one of the extra knee caps can be glued to the chest for a little bit more armor. Here's my unpainted take on it:
I didn't use the ethereal's legs for this guy, but both of these suggestions could still be used for a fireblade with those legs. They might even help hide the filing you would need to do to eliminate the ethereal caste symbol on the chest plate.