Somebody asked me this question. For sure, professionalism dictates that standard R/T is used, but is there anything preventing the casual weekend pilot from making up his own R/T as he goes along? I've been looking through the documents and can't find where it says pilots must use standard phraseology. ATCO's need to follow the rules:
JO 7110.10T 14-1-3. WORDS AND PHRASES
Use the words or phrases in broadcast, radiotelephone, and interphone communications as contained in the Pilot/Controller Glossary.
Any such thing for pilots?