The problem with doing that is when the connection is quiet, all clients still only get 2Mb.
You could look at doing something like this to ensure a fair service to all, it creates a queue called default-sfq (as my OCD doesn't allow a hotspot or wireless queue on the WAN), target could be your PPPoE interface or you could specify your /24 with destination 0.0.0.0, max-limit is download/upload.
IF the connection is at full utilisation this gives a round robin approach to packets.
/queue type
add kind=sfq name=default-sfq
/queue simple
add max-limit=55M/15M name=WAN_Queue queue=default-sfq/default-sfq target=pppoe-out1