hope your ID is well versed in landed house regulations.
whether you can get approvals within 6 months or not depends on how many times your submitted plans get rejected. URA takes about 1 month to check and approve/reject. So if your submission gets rejected, the same process and wait time is repeated. Usually BCA submission is done after URA approves of the plans. BCA side wait time is shorter (last time standard is 7 working days) but of cos if reject then repeat same process. One thing you can "help" is to pay up promptly as soon as you are requested to pay for the submissions. Cos the authorities will only start processing upon payment. So if you take you time to pay then they will also take their time to start processing.