Your idea of "prospecting" follows the setup of an outlaw motorcycle club...the Widows Sons are a motorcycle riding group, and are much less formal about membership and patches, although we do have specific requirements for membership eligibility.
My Chapter (Shasta Craftsmen, Northern California) wear a different patch than the one you posted as the back piece, but we also wear a round square and compass patch above that. It's that Square and Compass patch that unites us in masonry, not the Widows Sons patch (thank you Bro. Moffet for that).
We do not "earn" our patches and rockers in stages like an outlaw club...we buy them and sew them on. It's that Master Mason Degree that binds our members in fellowship. If someone wants to join just to have a fancy backpatch, then they are joining for the wrong reason.
Membership should be clear in the Grand Lodge's eyes. Master Mason only if you want the GL to give their blessing as a full Masonic organization. We do allow associate members who are not riding members, but who are interested in helping and supporting the mission of the Chapter (that was the issue for the Grand Lodge of Texas), but Associate Members do not (and should not) wear the patches or participate as a full member does as far as riding and voting (they don't ride and they don't vote).
I support having Entered Apprentices and Fellowcraft who ride motorcycles to come ride along with the Chapter as guests and even attend the meetings as non-paying, non-voting visitor of they wish. This gives them an incentive to get themselves to the 3rd degree and join to become a full member. Heck, even a non-mason guest should be invited...it may spark an interest in masonry. Once they get their 3rd degree, they are invited to join the Widows Sons as a member. No need to do a prospect program with one or two patches and complicate matters.