Strictly speaking, there is no Holy Saturday Mass.
There is a long vigil service, culminating with the Easter Midnight Mass, but no Mass on Holy Saturday.
While we're talking about Liturgy, I'd like to remind everyone that the Liturgy during Holy Week is second to none, being the most ancient in current usage.
Notice certain "changes" during Holy Thursday Mass? Those aren't changes; you're looking at a time capsule of the Roman Rite Mass before those things were added over the centuries.
And yes, the Church can make small changes to the Liturgy. We "trads" have had a bad experience with the Church changing the Liturgy, but we must realize that under normal circumstances the Church can add this or that small feature to increase devotion or combat heresy. The Church does have that power.
What the Church can't do is throw out an entire Mass and make a new one up from scratch, using heretical services as a template!