what is the business reason or exact use case behind your need to do so? Honestly I don't understand why this would be a requirement.
the customer needs to see some lookups differently.
In particular, lookupValueCustom will have more fields on LookupValueLang.
Is it possible to see two different lookupValue structures on client?
can you share a practical example on a business case where this comes into play? Having a small example always helps to make sure suggestions match possibilities :-)
However, having a custom lookupValue in parallel is not possible. The enumProvider is hard wired with the lookupValue that is there out of the box so it would require a complete own UI, etc. for the custom one.
On a first thought I only see two other options:
1. Activate reserve fields as needed in the generic lookupValue: Downside, those fields are visible on all lookups
2. If you need to do something custom you could actually use dictionary or genericdata as well instead given my concerns above.