I think this is going to come down to the nature of the ingredients and what it is you're doing with them?
Assuming the alternative supplier(s) are assessed and approved via your usual system in terms of food safety etc, your main considerations in terms of equivalence of the two sources is going to relate to what those ingredients do/don't do in your recipe(s). If you're wanting to put together a checklist for this then it's perhaps worth sitting down with a team of people spanning the relevant departments in your business.
For example, the product developers should have a good idea of what the key organoleptic attributes might be, and what quality-related analytical parameters are most significant.
But your colleagues in production may not care if the ingredient is functionally identical if the new supplier can only provide it in 10g sachets instead of the 25kg sacks they normally receive it in, as it adds an inordinate amount of labour requirement to the actual manufacturing activities.
Or logistics and supply chain may agree that the ingredient looks like it'll do a lovely job, but if the incumbent supplier provides an ambient material and the new alternative is frozen then they probably need the opportunity to consider whether you have the required logistics/storage capacity in place.
You might even need to get sales involved (we do), as there may be some unavoidable changes that could impact finished product, so they'll need to sort that out with their customers.
Depending on the size of your business and your suppliers, you might even need to get finance involved as e.g. a change in payment terms could have an impact on cash flow.
TBH this sounds like the sort of thing that lots of departments would like to be an issue that resides solely in the technical team, but should really be a group decision with input/consideration from various departments
If they're insisting that you are the person to write the checklist, I'd still go through the process of speaking with each department to get their input so that they can't turn around and blame you if/when something that causes an issue for them gets missed...