Right now, import option is optimized for calendar-end renewals (used it on this site), not for fixed-time type imports. But should be able to be added easily. Please contact me after release if it's not included in initial release.
Just a small thing but important for us down under. No doubt you've factored it in already. But we sometimes get addons with currency shown only in US$ UKpounds or Euros. Accommodating local currency is important. Paypal takes care of this in payments but we like to be country friendly in the general information/presentation of what we offer. Being able to add AU for Australian dollars would be good.