Hi Michael,
Sorry for the late reply.
1. Limiting guests – as you’ve probably noticed, for the moment we only have “Block guests” option. The idea of limiting it by email sounds interesting, but it may be quite complicated to implement, as now our plugin stores sales data in each user’s meta, and as for guest there is no user in DB and thus no meta, we will have to store sales data differently for them. Anyway, I will have to look into it further – will get back to you asap. By the way, if we are going to limit it per email, it would be probably a good idea to verify user emails with e.g. Email Verification for WooCommerce plugin.
2. Limiting per order – these two plugins should cover “per product” and “per order” functionality:
* Product Quantity for WooCommerce
* Order Minimum/Maximum Amount for WooCommerce
I understand that installing one plugin is always better than two (or even three), but to be honest, I’m not sure if I want to add it to the plugin. Again, I will have to think this through.