Hi,
If you used the items and recorded transactions already for the last three years in AX - even though without any valuation usage - I would not simply try to switch those items and try to change their
stocked/unstocked type or nature but rather create new ones.
What confuses me still is the fact that - on the one hand side - you want to change your items to non stocked ones and - on the other hand side - use MRP. Is that right?
I would suggest that you have some internal discussions first with your MRP/production colleagues before making any change to the current setup. To me the overall strategy of this item change does not feel being consistent and suitable to what you try doing.
Best regards,
Ludwig