I imagine that the calendar based on round numbers will be attractive to Sanhedrin. For one, it keeps the Psak of the gemara in Rosh Hashanah 21, according to which the latest date the Spring Equinox is Nissan 16. Second, it is an eternal calendar, which goes to generation five in the year 6000, 3600+5*480. This is easy to remember.
The Qeviyot of this calendar can be found here, until the year 6500. The complete Java program is here.
