P&P Grand Mastery: Possible?

I would like to make a small P&P proficiency mod but I'm not sure whether P&P Grand Mastery is technically feasible. According to the AD&D Player's Option (Combat & Tactics) manual, Grand Mastery grants +1 attack compared to Specialization (which we know is possible from the un-nerfed Grand Mastery component in Tweaks Anthology) and increases the die size of the weapon by one (e.g. a long sword in the hands of a grand master would roll 1d10 for damage instead of 1d8.)

Is the die size increase something the engine supports (and if EE supports it, does vanilla)?

The flat +2 damage bonus currently granted sort of mimics the effect, but it's technically more powerful (as it also increases minimum damage) and frankly less flavorful.

High Mastery would also need changing to grant -2 Speed Factor and +1 Critical Range instead of what it is currently doing, but that's the same thing a pip in Two Handed Weapon style does so I know it can be done (what I don't know is whether High Master and Two Handed Weapon style would stack, which they should, but I assume yes.)