We need to understand one issue here first: Differences between H4 and F1.
H4 can take courses at any time as well as take no courses at all. H4 can take one course or two courses, which totally depends on how you want to do it. However, F1 doesn't have choices. F1 has to takes coures except for OPT which is an early issue to you. F1 has to take credits as required. If your I-20 is approved this year and will start next Jan, you need to take courses, otherwise you will lose your status. You are right on this point. However, If your I-20 is approved this summer and you will start your student status next Jan, you could be in trouble. So timing is very important to you. I strongly recommended you take courses in the fall 2012 as a full-time H4 student in case your F-1 was approved in early fall.
Let us see if Bodd and other masters have the similar opinions. This is just my personal experience. I wish you good luck.