i can understand both sides of the argument
The Relic section say a model may replace One of their weapons for One of the following. Which by the wording used means only one can be selected per model.
There is outcasts viewpoint on it but
You could read this as being a limit that a single model cannot swap a single weapon for multiple relics, ie i will swap my chainsword for a burning blade and a shield, but while they have multiple weapons they rinse and repeat any one weapon for any one relic.
like it has been said it is open for interpretation. one may be the obvious interpretation for some, the other may be the obvious interpretation for others.
the simple fact is with the sentence as it is written a model are limited to swapping 1 weapon for 1 relic. BUT the way I read it there is limiting you from doing this multiple times for the same model.
NOTE: i have not checked the codex this is based on outcasts' post of the rule.
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