How effective is this new special defence going to be?
Several profs will have moderate specialization in it, with only a handful being proficient.
The issue, or concern I have is that some profs who already have a WELL established defence, will gain an unbalanced gain in defence when their defence is already established, just due to free IP.
Those who need it most:
TL4 shade, MA, keeper
TL5 shade, keeper
TL6 shade
TL7 MA, shade, possibly keeper
Those who DON'T need it:
TL4,5,6,7 Enforcer, advy
So, how maybe a good question to ask is how will the special scale?
Clearly some profs who do not need it will have access to it, and, how will their defence be augmented by the special if FC deems those profs not in need (as I have mentioned but not given evidence for).
My preliminary suggestion for this is that the special is inately stronger for specialized classes, (MA, Keeper, shade), and, the special itself checks both prof and skill AND TL for effectiveness.
While it might be tricky to code, it's important for balance.