Maybe using a couple of uncoated filters on the lens would help. They could reduce contrast in at least some situations without much effect on clarity. I think it would do as much as removing the accessible coatings on a lens, which would be difficult to do while maintaining a high degree of polish anyway.
Other than that, just using older lenses would the most logical. As you're saying it's the way light is channeled to the film, I don't know that modifying any modern lens will give what you want. Reducing contrast by removing the outer coatings on a modern lens won't do as much, in my opinion, as having a couple of uncoated filters on the front of it. If you're trying to remove all or most coatings from the elements, that just seems like an awful lot of work, and it will still not "channel" light differently, except for increased flare.
Some say part of the old lens look is due in part to the designs, which had less complete aberration correction due having older designs and the need for fewer elements to avoid excessive transmission loss and contrast loss.