I've been searching for a thread discussing this specifically for a while but didn't find one after a while of searching. I would like to be able to send retainers to specific content I've been to and cleared before.

I wouldn't include things like current trials and raids, but being able to send a retainer to just a zone or a dungeon or old trials and raids to collect things in said zone would make for a great change in my opinion. Some people grind forever to get one piece of glam from a previously level capped dungeon such as Swallow's Compass from Stormblood. While it makes some sense for current dungeons not to be included in the dungeons you could potentially send retainers to for equipment level reasons, we could end up sending a retainer to those dungeons for the sake of eventually getting the piece of glamour since retainers as far as I'm aware don't bring you something you already have in your main inventory. We have this type of loot system in the levelling dungeons, but if we can't have it while running the dungeons ourselves, why not send retainers to them? As far as trials and raids go, maybe having a higher chance at getting materials that you would obtain from desynthing equipment would be higher chance to obtain, but also having the small chance that they could bring back rare materials or old content equipment that could be used for glamour or be desynthed for levelling desynth. This would obviously require the instances to have been completed, such as fully completing the raid series to send a retainer to collect from the raid series.

This could also work for open world zones. Imagine your retainer being sent to the Lochs and bringing back a map material from Stormblood maps, or the same for Heavensward and A Realm Reborn. Shadowbringers and further expansions as well. Bringing back allagan currency pieces or bringing back random mob drops from the areas would also be a chance for the retainers to bring back.

All in all, I would like more options for where to send retainers. Perhaps each venture could take an hour every time and never diminish in time like the quick ventures. I would also like this to take dungeon equipment out of the quick venture loot table, so to provide us more chances to obtain rarer loot from the quick ventures, but that's a big ask since other ventures don't remove things from the quick venture loot table.