In our setup the limited selection of start dates in the deferral templates also prohibit the use of deferrals. So I would like support the OP's request for an expansion here.

In our case most deferrals would run over a calendar year. If an additional option 'Beginning of next Calendar Year' could be added (to the Start Date dropdown in the deferral template) we would be very happy.

I cannot imagine it could be too difficult for Microsoft to add a calendar year to the dropdown. However, doing deferrals by hand in an extension by putting the amounts on a G/L account and performing the deferral manual is infinitely more complex and in the end still a hack of the standard.

I can imagine other companies might benefit from a 'Beginning of next Account Year' option as well.

But I do admit that in some cases a custom start date and length in months for a deferral would even be better. I can imagine that is more complex to realise in the BC standard. In any case that change would only cover a very small percentage of our cases. So at least for us (but maybe not the orignal poster) a calendar year option would solve most of our problems with deferrals.