A quick google search seems to imply that "Modern Egyptian" is not
exactly a conlang. Rather, it seems to be a transliteration of Coptic to
the latin alphabet. This is all based on the only relevant google hit
for "modern egyptian language", so "Prince of Egypt" should feel free
to
enlighten us if this is incorrect. The site is:
http://www.geocities.com/remenkimi/
Specifically:
http://www.geocities.com/remenkimi/KTS.html
According to this site, transliterations of Coptic into Arabic have been
performed for about 250 years, and transliterations into the latin
alphabet have gaining in popularity over the last 50. The "Modified
Isaac's Transliteration", or MIT, was referred to as "Modern Egyptian"
in the seminal book on the subject, published in 1999. This was intended
to allow people to easily type Coptic with our western computer
keyboards and typewriters, and to make learning easier.
Information on the cultural value of Coptic is at:
http://www.geocities.com/remenkimi/stshenouda2.htm