One thing that might stand in the way is that every single existing particle parameter takes the form of [PARAMETER, VALUE], which makes the whole lot traversable as a strided list. Even the stuff that looks like multiple values, is a single value made | up | of | bitmasks.

I'm not against alpha-masked particles at all. But it might need to take a different form to maintain some semblance of consistency.

Perhaps something like [PSYS_PART_ALPHA_MODE, PARTICLE_BLEND_MASK], and [PARTICLE_BLEND_MASK_CUTOFF, maskValue]. Something similar in any case.