No, it's not a bad design per se.
You have three options:
* Redesign your board to take a normal SMD module. Be sure to find one that comes on tape or in tubes, otherwise you're still out of luck re: volume production.
If space is the issue, you may consider soldering the SMD module on a custom PCB, which is then mounted vertically with a connector of your choosing. This obviously adds rather a lot of cost.
* Deal with just hand-soldering it. Really, 500 pcs is still manageable, if a bit tedious.
* Have it professionally wave-soldered. If your board has other through-hole components, this of course makes even more sense. If you have SMD components on the bottom (double-sided load), you will have to either re-design it or to pay extra for selective wave-soldering.
I'd also like to remind you that these modules are a bit iffy. If you're doing a commercial product - and it sounds like you are, wrt. volume - you will need the full EMI/RF compliance tests. Yes, even if the module sports a fancy FCC logo. This, incidentally, costs money.