With buy-side clients taking on multiple brokers for execution and clearing, FCMs will have to become specialist service providers.
Williams departed State Street in May after the custodian announced it would shut down its global FCM business.
State Street announced the closure of its derivatives clearing business in March as it looks to refocus on core businesses.
IDX panel says clearing banks need new tech to cope with impact or capital rules.
Buy-side firms may struggle to access markets as banks withdraw from clearing services.
Latest CFTC data shows a major drop in the number of US futures commission merchants offering services to the buy-side.