Shop App question(s)

I've been looking at various Web Hosting Billing services and have found them to be vastly inferior to Perch in terms of their flexibility with respect to generating code, as well as importing and exporting data.

Maybe this is because they are a billing system first and CMS second but integrating one with an existing site, i.e. Perch is not really something I wish to burden myself with at any stage as I'd much rather re-model an existing Perch site, what I call a "template" (basically PHP code interspersed with .html templates, rather than just SQL data extracted via PHP) and introduce plugins from there.

My question is, does the shop app allow for invoicing in the vein of say how PayPal allows arbitrary invoices to be generated?

Also, can subscriptions be created such as with the provision of web hosting?

Thanks for any information.