You can split recurring subscription charges by creating additional pricing plans for the same product that is split accordingly, then assigning the plan multiple times to the customer with the apprpriate billing dates. For example
Product: Coach Ryan: Remote Coaching
Pricing Plan: Coach Ryan: Remote Coaching 12 month: $300
Split
Pricing Plan: Coach Ryan: Remote Coaching 12 month ½ Split: $150
Bill Date 1: 1st of each month
Bill Date 2: 15th of each month