Agree with Robert about checking the whole package, not lock up periods.
These - like other rules - have changed recently and firms may not be in favor of them, but have to comply. One example, Bright has max payouts because of its clearing deal with GSEC (who had to comply with FINRA rules). Bright isn't FINRA and didn't want to do it, but didn't have a choice.
Well capitalized CBSX firms - some at least - did not use capital contributions from members for trading capital, but on October 1st, 2010 the CBOE put out a memo which said they had to going forward.
In a nutshell, because of some scuzzy CBSX marketing pitches to retail (etrade, schwab, amtd customers) using a sort of loophole with no licenses required, the SEC put pressure on CBSX to require this to make it less like retail.
Echotrade's SRO is the Phildelphia Stock Exchange, so they still require 7's but don't need to require lock ups etc. I don't know if they lock up or don't lock up money accross the board, done right, it can be done on a case by case basis.
Gut here - the Series 56 will be required across the board for prop (the 7 will get you a waiver), and that for prop, lock ups will be required... But who knows how long that will be...