Illumar buttons are nice, but it would be an excellent feature to be able to illuminate them using a redstone signal, e.g. supplying a weak signal (via creative redstoning) to light the button, but reading a stronger signal if/when the button is actually pressed.

Not sure this is the intention of the button. The button is only a power output source, it should not react to redstone input. The Illumar buttons glow as feedback for pressing, if you want to show redstone power then use a lamp.
It's @MrTJP's call though being the creator/designer of this mod.

Because it only took a few minutes, added via bf9602c