I don’t think it’s “Protestant”, especially if the cantor is coming from the choir, which happens a lot, especially in one cathedral I worked at and at a number of cathedrals where I’ve attended mass. Many choirs at Catholic churches use choir robes, so it makes sense that the cantor would wear one as well, unless, of course, the cantor is a seminarian or deacon. I’ve seen organists wear the cassocks, but that I’ve actually heard people refer to it as “too Protestant”, but personally I think the wearing of cassocks or choir robes are fairly neutral to me in terms of lay people wearing them. You also have to realize that as a cantor, you really don’t have a choice if the pastor or the music director is telling you to wear something. Most of the time, cantors really don’t have much power. haha! (We usually don’t have a say in the music either, although we tend to be blamed constantly for it, when it’s really either the priest or the music director/organist.) So, even if I did feel that it was too Protestant to wear a choir robe, I couldn’t just go and wear an alb, especially if the rule was I had to wear the choir robe.
That said, where I have my main cantor job, there are no robes or albs for me to wear, which I think is fine as well. I always try to wear neutral-colored, modest clothing so as to not bring too much attention to myself and that includes with how I sing. (ie. I sing in a more sacred, subdued way with my classical training, even though I can and do sing like a trained opera singer for my outside opera gigs) I think most of the time, I’ve done my duty with that, based on what I often been told which is always wonderfully humbling and helps me always stay focused on the prayer. I’m sure you can’t please everyone as I know some people don’t like classically-trained singers and some have assumed the worst in us, but I know I’m doing my job well and without ego.
Quite honestly, my preference would be to sing from the choir loft, with the exception of the psalm and gospel acclamation. Because, really, I rarely, if ever look at the cantor for direction as to when to come in to sing a hymn or the parts of the mass. I don’t even look at them for the responsorial psalm or gospel acclamation. The organist should be able to lead them with how he/she does the introduction before the congregation comes in. I know that many people who aren’t musicians do the same. The instrumentalist really is more important with leading the music, in my personal opinion, although a good, well-trained cantor and/or choir can add the vocal prayer to it. But that is all for another thread.