TDA allows purchases of pinks with stop sign. Also, you need account balance of => $25k to avoid the 3 day clearing cycle. No margin on pinks. Above is on cash trading accounts. Not sure about IRAs.
Stop signs have never been a problem. I must say I've had the account for a number of years and prior to reaching 20k balance and 30 trades per qtr I also had up to three days delay. However when I cashed out most of my profits from $hmp last year they still gave me no hold status with my funds when my acct. fell below 20k.
I my be grandfathered in but you might check out E Trade Pro.