If you gave Weeblers only one wish, I would put my money on "more themes". Weeblers are now seeking outside providers to add some "sexiness" into their themes and willing to pay up to USD60 for a theme.
Why don't you (Weebly that is) ride on this gravy train and address your Theme-deprived position. Let us face it your option for themes is not considered to be the most competitive advantage.
May I offer some solutions:
Take over (buy that is) some of the up and coming 3rd party theme providers (by the way I do not own nor work for any 3rd party providers)
If your funds are limited then, create a revenue generating division and compete with the third party theme providers - but offer themes at 50% cheaper than the comparable 3rd party providers.
This division will soon bring in incremental revenue before you know it. I am certainly going to be one of your customers.
I am sure Weeblers would rather buy from Weebly than outsiders simply because of your support service and future compatibility.