Hello ngie, you can actually speak to the wedding coordinator of GPCH to get them to make tentative booking for your preferred date. If other couples are interested in your date & are willing to pay the deposit, the coordinator will call you to double check whether you are still interested before they give the date to the interested party.
I believe you must have been to those 5* hotels right? Yah, some of these hotels would require a large percentage of deposit. I would rather not pay that much, as sometimes, we are not sure whether there's any last minute change to the wedding plan & I have seen many couples trying to transfer out their package at a huge loss.
I think I saw from the previous posts regarding the wedding show in September, but I am not sure how confirmed the event is. You can always check with GPCh lah. It's good to have more people joining GPCH, so that this thread will not seem so quiet.