If we use the Shopify Plugin for WordPress, would this work properly with Modern Retail's integrations?
Currently, we’re still gathering all the requirements, but they are thinking they want a site to be a heavy content site with a dedicated community around it and a large e-commerce site. They also will need 24/7 support for e-commerce, something WooCommerce does not offer.
So because of this, I think we would have to go with a WordPress-based site with a Shopify plugin (acting like a portlet) to the back-end hosted Shopify application. We’re still finalizing our investigation on this though.
At some point, they’ll need to come to a decision; either go very e-commerce and little content or vice-versa.
This is the first time I have heard of this plugin. My initial reaction was to turn my head sideways a bit and ask why would anyone want to do such a thing. However, if you have a client who's an avid fan of WordPress.com and has basic e-commerce needs, then this could be a good solution. However, I highly recommend that you give your customer a custom domain at wordpress.com, please read:
Failing to do so could destroy their SEO if they wanted a custom domain in the future.
Now to actually answer your question; yes, I see no reason why our Integrators would not work in this scenario (e.g. we are communicating directly with Shopify's API, so it really doesn't matter what technology is running the front-end given we're talking with the back-end).