So, I thought it didn't really make sense that only heretics have access to Legacy Weapon rules, as astartes live for centuries too, often using the same implements their entire lives, or performing spectacular deeds with a single weapon over and over again. Of course, this would only be compatible with standard issue/signature wargear. My question is, since the tables don't really make the most sense given their tendency for "hate" etc, how would one go about reworking them? So far all I've done is say "you can have this quality for this weapon if you take it as a Legacy Weapon".

Legacy weapons are supposed to be the bonding of man and weapon fueled by the corrupting powers of the warp so I don't think it makes much sense to translate them. DW marines have access to relics which are holy items they are supposed to aspire to being worthy of. There is a big level of humility difference there. The idea of new holy relic in the making looks good on paper - until you realize that the process is usually finished posthumously.

I'd require a Legacy Weapon to be a Signature Wargear item, even if it's also something they get as standard issue to represent that it's not just any weapon. Maybe using Renown instead of Infamy.