GreaseMonkey Gearwork, Grimdark Gentleman, Grimdark Lady, Hazel Cassandra, Lililace Gilded Masque, Mimi Moe Lockwell, RoQ Candy Boudewijn, RoQ Candy Ventura, Sougara Yun, and I'm sure I'm missing a couple or so, are all Masq lines. Now, with that being said, those are a lot of lines to put back into circulation at once LOL! XD We had the Grimdark and I think Greasemonkey unretire last year. It'd be nice if two or three different sets could unretire this year and make it a rotating thing annually.

Yeah, this would be kind of nice, but only if most pieces in a set went above a certain price in user shops or something. There are pieces in some of these sets available for under 1m (though I didn't, and am not going to check everything, so some of these sets could be expensive enough that I'd support bringing them back)
Hazel Cassandra, Lililace Gilded Masque, Mimi Moe Lockwell, RoQ Candy Boudewijn, RoQ Candy Ventura, Sougara Yun etc were all ordinary subq lines that stuck around for a long as any other line. I think they've had their time. There's no precedent for unretiring old lines, and I think it's reasonable to keep it that way.
I can see a point for bringing back Greasemonky and the Grimdarks, but it also might be nice to give them a rest for a year or so.
Are these pieces from these lines that are absurdly priced? Like, 10M or more?
GreaseMonkey seems to be the only line with some higher priced pieces. Everything else is still affordable, and unretiring them will just make it harder to get pieces from more recent and/or desirable lines.
I don't think any of those sets should be unretired.
As said, most of those lines are normal subeautique lines and I don't think they should be unretired since they were never limited edition like the GreaseMonkey and Grimdark lines. But even for GreaseMonkey and Grimdark, all the items are available in usershops. The vast majority of items are all under 5m. It's not like they're super expensive or limited. I think there were only 2-3 items that were over 10m, but they were still under 15m.