Found a sneaky bug in your addon. Your overloaded Actor:getObjectOffslot() includes the following code:

if o.dual_wieldable and self:attr("allow_any_dual_weapons") or self:attr("hulking") then
	return "OFFHAND"
else
	return o.offslot
end

As written, this allows the player to wield literally anything in the offhand slot once they have the Hulking Berserker evolution. I tested this by dragging the transmo chest into the offhand slot on the inventory dialog, which it accepted without a hitch. I think you need at least an 'o.type == "weapon"' check in there.

(This also plays high holy havoc with Enhanced Object Compare and Enhanced Wield Replace, both of which key off which slots an object claims it can be wielded in — and with this evolution in place, pretty much everything claims to be wieldable in the offhand slot.)

And purely as a wishlist item (a quick code check didn't find an easy way to implement this), it would be nice if damage done with dual-wielded two-handed weapons could be recorded as both two-handed weapon damage and dual-wielded weapon damage for purposes of prodigy requirements. My Windblade hopes for this character have been cruelly dashed… :(