Dear Sir,
I have read everything & consulted with my technical team lead, so my team said that this solution can be delivered easily using OpenCart but if you still want Shopify, then no problem, because Shopify is just a builder, while using OpenCart, we can easily customise it according to your functionality.
Please let me know how do you want to proceed, as I can also give you our team high level understanding paragraph to make sure that we are both on the same page in terms of requirements understanding.
Just so you know I am flexible in prices, as quality & long-term relationship is more important.
Look forward to hearing from you.
Regards,
YK
LEADconcept
PS: Please let me know, if you want to see some of our recently designed/developed Websites.