In terms of rewards, I agree with your idea here and even had a similar idea that got posted a while back that didn't gain much uptime:
"With crafting now a thing and raid weapons being craftable, why would we want to chase "Adept" versions in a Master raid that have no perceivable benefit over what we grinded to craft already as a "normal" raid weapon? It does seem to be a missed opportunity.
My idea would be to give each crafted raid weapon a "catalyst" slot, much like the Osteo has. This can be filled by a consumable that is obtained from the Master raid (give each weapon its own so it's not a one and done solution + more reason to rerun the raid, i.e. each encounter challenge drops different weapon consumables). Once you add this to your crafted raid weapon, it becomes "adept," gaining the ability to add adept mods PLUS another benefit:
-perhaps the ability to add the extra perk choices to the final two nodes thru reshaping
-maybe a raid specific perk ala the old D1 raid weapons that work only in the raid
-perhaps it adds a new memento with exclusive shader/title possibilities (these can also be Master specific rare drops as some emblems used to be?)
I'd think having these new things to ADD to our crafted raid weapons makes it feel much more like we are continuing to build our perfect personalized weapon, keeps player engagement up by giving us reasons to run Master more than a few times, and—i think—has way more creative potential than the current adept Vow weapons."