If you are using support partners the standard setup is to split the revenue with them (typical splits range from 25 to 50%) but a better idea would be to build a reward system based on performance. Say the partner usually gets 25% of the support revenue. What you may want to build is a system through which partners that escalate a smaller portion of their cases and/or achieve high levels of customer satisfaction get an extra “bonus” based on performance. The bonus would be a back-end (after the fact) payment, unlike the revenue split.
In most instances the issue will be measurement: how can you capture the escalation percentage, or customer satisfaction accurately? Focus on accurate measurements so that the incentives can work properly.