The Mass is a latin language, hence the use of spirit. Besides many people (and children) would be concerned with saying ghost.
That’s just it. Much hay has been made of the change of translation to “your spirit” rather than “you”, not just because there is a Latin cognate of the word spiritus, but because it somehow “recalls an ontological change of the clergy” in the response.
The term spirit is pretty ambiguous, actually. There are spirits in a liquor shop, and yes we know the difference! But how about use of the phrase “That’s the spirit!”, or “Spirit of St. Louis”, or everybody’s favorite “the Spirit of Vatican II”, or “spirit vs. letter, of the law”.
Suddenly spirit is mere motivation or willpower, or anything that can evaporate quickly without being a visible gas! Inanimate objects and concepts now have spirits. People have collective spirits.
If we wanted to hammer home that we acknowledge (and reverence?) some mystical quality about an individual clergy in our response to “The Lord Be With You”, that is distinctly non-corporeal and individually human, why not use the word “ghost” in English, in the same way that I believe in German the response is “und mit deinem Geiste”.
Yes, “ghost” elicits a viceral reaction, and images of Casper and bedsheets and Halloween, but even those connotations lead us to an awareness of the soul, much more than “spirit” does. If we want to elicit a thought-provoking response in the assembly to educate them (like the way that “consubstantial” is defended), I think we would do well to consider “ghost”.