While they also don't pay interest on cash balances, Tradier's REST API looks good. They also have a cobranded $40/month unlimited options trading offering at http://try.tradier.com/steady-o-013/
OK, so with quick searches I see management fees of ~1%(+) and a $4800 flat fee:
http://www.ghpia.com/process-and-fees/fee-structure/
https://www.advisoryhq.com/articles/financial-advisor-fees-wealth-managers-planners-and-fee-only-advisors/#Flat-Fees
http://www.basonasset.com/our-fee-structure/...
Read the broker disclosures carefully. "Smart" orders are likely partially PFOF driven, and I wouldn't be surprised if DMA orders would fall under PFOF too ...
https://jellifin.com/ now has $25/month unlimited covered call, long put/call trades.
Their broker is https://www.thirdparty.com/ https://brokercheck.finra.org/firm/summary/144076