I'd suggest putting your entire Design Data folder in a central location & pointing to that from your project setting. Yes, set the InventorMaterialLibrary.adsklib file under the Materials folder to be read-only. Put your custom adsklib there too & set the permissions on that for only those who are 'supposed" to be making changes.
If you use vault you can go one step further & check in the entire Design Data folder to vault. Then if you need to make changes then you can check out the appropriate file(s), modify & them check them back in, so that those on disk are left read-only. Many customers currently do this with good success.
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