ASL is a different language with its own grammar and syntax. It is much more than just a collection of signs. It would be considered very rude to tell someone speaking ASL that they are “leaving out words” or using a “simplified and abbreviated version of English.” ASL can convey very precise information as well as rich, expressive poetic thoughts.
That said, there are different skill levels of ASL users. If you grew up speaking ASL from birth (and I know many people who have), and you spend a lot of time regularly in a large, diverse community of ASL speakers, and you are educated with the resulting educated vocabulary, then its one thing. Of course, many people who know some ASL are not proficient and it is their 2nd, 3rd or 4th language. Like any other 2nd language, they can make themselves understood, but the native ASLers are being very lenient. You are most likely mangling their language, but they will catch on to what you are trying to say.
There’s even “baby ASL”, which is signing for infants. As there is a certain dexterity required, and infants lack the fine motor, they are taught an abbreviated version of ASL. I’ve seen many adults talking “baby ASL” and not realizing it!
All this is to say, there is no reason that all the rubrics can’t be covered by ASL. If necessary, and is often seen, a person may finger spell important words to make sure the correct thing is understood by all, or just to emphasize something. There are many nuances of body language to connote things that we might use “helper words” in English.
I have attended Mass many years ago at the deaf community parish in San Francisco (which is a striking church by any measure). This was a lunch time Mass, so we were about 1/2 hearing and 1/2 not. Some of us spoke the responses, some signed and some did both when we could.
I’ve also attended Mass in other foreign languages where I hardly caught more than a word here or there. I just responded where appropriate in English. It is one of the wonderful things about Catholicism, isn’t it? During the homily, I meditate on the readings until we are back on safe ground. If I were to attend a 100% ASL Mass with no spoken language, I could follow along and I would simply do as I do in foreign language Masses - respond when I know where we are, and tap my missal and look puzzled at my neighbor when I need help figuring out where we are.
There are some awesome ASL translators in the Bay Area. I was watching a video my brother (a protestant evangelical) showed me of his church with ASL, and I was struck at how simplified and babylike their translation was compared to what we are used to here on the West Coast.
If a priest can be ordained who speaks German, Spanish or French, then there’s no reason he can’t be ordained speaking ASL. Not every deaf person can make intelligible oral responses, and for something as important as an ordination, he should be allowed to speak in his first and native tongue - which is ASL for many people.
Hope this provides a bit of insight.