While the new Tag- based mining tier system is much more flexible, it also comes with the large disadvantage for mods that desire to add mining tiers past netherite, they can only be compatible by adding dedicated compat for eachother.
This situation isnt ideal, so im suggestion the introduction of common tags to streamline that process.
My suggestion is to first add common tags that simply mirror vanillas tags :

minecraft:incorrect_for_wooden_tool	<- c:incorrect_for_tier_0
minecraft:incorrect_for_stone_tool	<- c:incorrect_for_tier_1
minecraft:incorrect_for_stone_tool	<- c:incorrect_for_tier_2
minecraft:incorrect_for_iron_tool	<- c:incorrect_for_tier_3
minecraft:incorrect_for_diamond_tool	<- c:incorrect_for_tier_4
minecraft:incorrect_for_netherite_tool	<- c:incorrect_for_tier_5

then maybe to add a couple tags that simply reference each other above tier 5.
This would allow mods that intend to add post netherite progression to tag their tool as c:incorrect_for_tier_6 or any other number and have compatiblity with other mods that choose to also add post netherite progression.
This wouldnt prevent mods from having parallel progressions if a mod wants that, but if compat is desired this would open a sensible solution for mods to use.
This also doesnt prevent mods from adding tiers inbetween vanilla, it might break the order up a bit, but post netherite the number doesnt matter, as just a system for mods to find eachother is needed.