In establishing a new company, let's say I wanted to make the Constitution date to another date? (instead of today's date) - Would there be a penalty on this? Or are there any implications?

A company can adopt a constitution before or after registration. If it is adopted before registration, each member must agree (in writing) to the terms of the constitution.

You can also check the link below to know more; 

https://asic.gov.au/for-business/registering-a-company/steps-to-register-a-company/constitution-and-replaceable-rules/