if the requirement is to generate quota only differently...you can look at contract type option on IT0016...instead of new employee ESG or PSA...you can try to maintain contract type on IT0016 for these employees that are going to get 10 days of CL...maintain QUOMO for these employees based on contract type...and assign them a new quota grouping...setup your quota rules to grant them 10 days of leave instead of 12
However if you do need them to have a different set of holidays then you will not have any option other than creating a new PSA so that you can assign an different holiday calendar, WSRs etc...