This would be really useful, especially if the rules can be configured for each leave type. Things like notice periods, holidays, carry-forward, and consecutive-day limits can get complicated quickly, so having them handled automatically would save a lot of manual work.
I have my own HR/ERP software that already includes a leave management module with similar functionalities, including leave balance, leave types, weekends and holidays, existing leaves, consecutive leave rules, notice periods, employee eligibility, monthly/yearly limits, carry-forward, and negative balance handling.