Omnivore for Marketplaces

Setup for the integration between Trademe & Shopify. I sell on eBay but Omnivore is a lot more expensive than alternatives so I keep it to trademe.
Omnivore is the only app offering an integration like this now Tradevine stopped their API however there are some issues:
1: Omnivore takes data from Shopify, not Trademe listings so all Trademe-specific data will be lost
2: No allowance for individual variant listings. These can only be grouped
3: No ability to have multiple product listings in different categories or different descriptions & titles - big downside results in SIGNIFICANT loss of sales
4: No ability to manage or answer questions
5: A big one - No website-based management area. Running multiple stores means we need to set up multiple apps in Shopify and to access Omnivore we need to login to Shopify and then access Omnivore for each store. Very time-consuming and sloppy
6: Difficult interface for managing listings
7: No feature to add question text across all listings or information on description pages (offered in Tradevine)
8: No integration-based refundability

My guess is Omnivore looks at Trademe as a very small market and is focusing more on other markets.

The upside is this is free software for the Trademe side of things and Trademe has basically no suitable solutions if you are a professional seller. If Omnivore made appropriate improvements this would be awesome software and I would be willing to pay for it

Very slow response, given the amount of money I have paid for monthly subscription USD 75, I have to wait for more than 24 hours to get a repsonse back (email). Cannot even dial-in to reach out to a real-person technical support, the contact number is always on voicemail

I have a love/hate relationship with this app. It is the only app I can find that does what I need. It has the potential to be a very powerful app, but it really struggles to capitalize.

Pros:
- It is free when used only with Trade Me
- Its core functions work
- It can import product metafields and use them (with some difficulty - template validation needs better documenation)
- It saves an immense amount of time vs manually listing products

Cons:
- User interface is poorly designed and outdated. Needs a complete rebuild using modern front-end techniques.
- Very rudimentary templating system that often falls just short of what you want to achieve.
- Many missing features, requiring complex workarounds to be set up
- Documentation is not complete and not always up to date.
- $75USD a month (+ commission) for the full plan is waaaay too expensive given the state of the UI and the lackluster feature set.

Edit: Happy to provide examples of issues to the devs should they reach out.