My suggestion is simple and comes in three parts.
1) A scaling item level requirement that updates to match the highest level duty within that roulette that you have completed.
If you've completed World of Darkness, then alliance raid roulette updates to now require that all of your gear slots be filled with gear, all of which are at the minimum item level for that duty (to wit: i90) and will not let you queue if any of your gear slots are unfilled or beneath item level 90. If you've completed Dun Scaith, then the requirement rises to i235, unless you're queuing for the roulette on a job beneath level 60, in which case it obviously reverts to iLv 90.
This same restriction applies to other roulettes, including leveling and normal raids, to prevent 'cheesing' into lower level duties by removing equipment, or actively griefing (i.e., it's currently possible to queue into Shadowbringers leveling dungeons with a level 1 weapon equipped)
2) Allow the creation of 'blocks' on the content of roulettes.
Every player character now has a limited ability to single out dungeons in the Duty Finder that they will never randomly receive, but only specifically when they solo queue, allowing them to specifically choose content which they will never be put into. The changing of these allotted duties should be limited to the weekly lockout, preventing people from simply curating their lists in between roulettes to circumvent the limited number available.
Ideally players should receive one 'block' at level 50, and another one for every 2500 achievement points they amass, giving purpose to the system.
Additionally, these 'blocked' duties should have no influence whatsoever on what you can receive from Mentor roulette, as the purpose of mentor roulette (and, indeed, all roulettes) is to fill queues.
There's a variety of ways to utilize these blocks, ranging from specifically avoiding level 50 content like LotA and Syrcus tower, pre-determining the destination of your main scenario roulette (thereby reducing or removing people that instantly leave upon the start of Castrum Meridanium) or for other reasons like specific, targeted aversions to certain pieces of content (motion sickness or psychological triggers in certain raids) but the freedom with which to use them is mostly left to the player.
3) A total revamp of Frontline roulette to a more generic 'PvP roulette.' Solo queue only, switches every 8 hours instead of 24 between 8v8 Feast, Rival Wings, and 8v8v8 versions of all existing Frontlines modes. The current, existing 24v24v24 frontlines are nixed entirely.
I don't really have a good reason for this one. I just think it would be funny.
In conclusion I'm all in favor of a system that gives more power to the individual player to curate their own experience, and I'm sure we all have a laundry list of duties we'd rather not be queued into for one reason or another. Thoughts?