such as "Rich 1, ready for departure"?!
The simple fact that you may be poor by the time you've taxied to the hold
Other than the universally used a/c callsign (omitting the country prefix in places like the US and Australia, where the chance of a foreign reg'd a/c in GA is remote), there are company callsigns. Every country has its procedure regarding the allocation thereof. So, if you wannabe Rich One (at least at startup), contact the CAA, they'll point you in the right direction
PS:
AFAIK, in most places, company callsigns are reserved for AOC holders (or equivalent) with significant traffic - one of the places I fly with uses them, and they are a busy FTO.