While there is no system yet in place for what you desire, there are steps you can take as CC owner to ensure compliance (beyond the honor system) with your request that "studs" do not enter below their tier!
First, make credit tourneys single play. That by itself won't defeat crashers.
Second, make tournaments of multiple rounds and threaten to expel any player who (even accidentally) enters below their tier! They can be extended a re-invite back to the club AFTER that tournament is complete. (By doing this, the player who entered below their tier gets a WD for the next round, thus eliminating them from winning.)
I usually run concurrent credit tourneys , one for master and below and another open to anyone (which will be dominated by legends).
For players which cannot compete with higher echelon tiers, I run (and self fund) CTTH tourneys which create winners for nearest over or under 250 for nine holes, but that requires examining all players histories because CTTH's are unlimited play tourneys. I could simply make the tournaments shorter in these cases. Caveat - since I cannot pay credits directly, these tourneys usually require I give away ball sleeves as gifts. Since I earn a boatload of credits daily by viewing countless ads, I can afford to do this periodically while the bumper crop of ads are running.
Lastly, in order to help players who are desperate to move up in tier (although I can't imagine why!), I run easy (free) tournaments which have even lies, low winds, green speeds of F or VF and I do it on Kiawah (which is easy until master level), Bethpage front 9 where forward tees (for lower tiered players) bring eagles into play, and of course, St. Andrews, because it's so universally popular. Remember, stroke CC tournaments already require that players shoot from their own tiered level tee boxes.
Fortunately, my group knows the value of the honor system and adheres to clearly marked tournaments.