OCO are convenient for bracket orders and exclusive entry for double setups. OCA is similar and quite useful for entering in different securities. Order attachment is useful for placing stop loss and take profit as soon as the entry order is filled (and those SL/TP orders need to be tied by OCO). I know IB supports this natively, but this could be made transparent to algorithms by having brokerage classes do this client side if server functionality is not available.

This is not a huge priority to me, since I can always create my own order manager, but I wonder if there are plans to support this.

Keep up the awesome work!