IMO, I feel it would be acceptable to offer such parts (1/72 scale black polyurethane rubber wheels), since they would fall in the "aftermarket customizing parts" arena, as opposed to the flat out recasting of existing parts still in production by the manufacturer.
On your first offer, maybe if you modified a Fastpack, adding a 6-barrel gatling gun or some other customization, THEN recast that as a custom add-on part for still available Hase Valk kits, that would be more acceptable. I'm sure such ideas have previously been discussed around here but I missed those discussions, so I don't know how other members feel about such customizing/casting of parts.