Sounds like you wish near real time email delivery. Enabling push maintains a connection with the mail server and provides immediate delivery. This appears better suited to your needs that 60 second sync polling.
Can you elaborate on the use case for a 60 second sync instead of using the push service? Enabling the push service provies immediate email delivery. This sounds like what your trying to achieve.
Thanks for the idea. However, this is currently not possible because the "high" minimum refresh interval limitations are being imposed by the device, not by Thunderbird.