I didn't know until now, it's too bad we won't be getting Bleoberis to help make Grand Ezel more consistent in GP over Gancelot let alone Tsukuyomi getting reprinted as an SP in Fighter's Collection 2014 which will probably raise her price even more. Bushiroad needs to release a set in Cardfight!! Vanguard that contains nothing but Sentinel units including Quintet Walls for every clan although it will become out of print just like with BT07 recently which raised the price of Great Nature quite a bit with Leo-pald Reverse and Chatnoir being the 2nd most expensive decks in the game next to Tsukuyomi.
Tsukuyomi is not expensive and hasn't been expensive or even popular for a very long time. You can see on ebay she only goes for about 6$ RRR and 30$ SP and even that's pushing it. Leopald Reverse and Chatnoir? They're 2$ each. Oh, and BT07 is still in stock in plenty of places.
A Sentinel exclusive expansion in Vanguard would still be a smart move on Bushiroad's part since it would help dramatically decrease the cost of running 4 Perfect Guards in every deck due to being mandatory staples. They also need to get up to speed by making sure that every clan in the game has Legion support since it seems like they're phasing out Limit Break despite releasing a new Grade 1 skill that enables clans to use Limit Break at 3 or less damage even though players nowadays are running 0 Heals so that they don't run the risk of sacking into a Heal at 4 when they want to get Limit Break off.
A booster of sentinel units would be silly, they're frequently reprinted for most clans and in set 16 and on they're not even clan restricted. There hasn't been a price problem like with Halo Shield Mark in a long time. All that booster would do is devalue the cards in general and slowly make bushiroad lose money. Every clan is quite obviously getting legion units, just like every clan got limit break units. They're just not going to do it all at once. I think they've actually been getting it done reasonably fast, all things considered. The grade 1s lowering limit breaks to 3 damage only serve as proof that bushiroad is NOT phasing out limit breaks, and on that note running 0 heals out of fear of missing limit break is downright stupid. Several limit breaks activate before the vanguard attacks, not after, and therefore are not shut off by drive checking a heal trigger. Even if you damage check it on your 4th damage and you're at 3 damage, you're left at an advantage regardless of limit break by being at lower damage. If you want to use your limit break early that badly, then run some of those self-damaging units that have been around since set 7, or those new grade 1s you mentioned yourself.
Another thing that Bushiroad could be doing to help improve Cardfight!! Vanguard is by releasing Trial Decks for clans that are unpopular in the Anime/Manga series being Tachikaze, Megacolony, Granblue, Bermuda Triangle, Angel Feather, Dark Irregulars, Great Nature, Neo Nectar, Murakumo, Nubatama, Spike Brothers, and Pale Moon. I'd also like to see Bushiroad go back to giving Oracle Think Tank more support other than Mystical Magus and the new Legion support for CEO Amaterasu and Battle Sisters.
Not every clan can constantly get trial decks. It'd be nice, but it would mean releasing way too many. You also have to keep in mind they have to keep them somewhat modeled after the anime for the sake of marketing. Despite this, we have still gotten a pretty generous diversity of trial decks already. Dimension Police and Genesis trial decks certainly weren't necessary to promote the anime but Bushiroad made them anyway. Clans are still getting support through main sets and extra boosters, and I don't think any clan is currently in need of severe support. Sets can only be so big, so yes, some clans will have more support than others at certain times, and some have legions while others don't. That still isn't a reason to print 15 new trial decks. OTT got two promo legions and an extra booster not that long ago, and they're still far more supported than, say, Megacolony.
We all know that the main principles to win in Cardfight!! Vanguard are Pressure, Advantage, and Consistency but what about Defense as well? The game itself needs more units whose sole purpose is to defend your Vanguard rather than just adding more unnecessary pressure to an already pressured opponent. Grade 2 Interceptors that Intercept for 10k instead of 5k or even units that work like Starry Skies Liberator, Guinevere for every clan that functions off of Sub-clan names like "Blau", "Ezel", "Amon", "Revenger", and "Amaterasu".
Try playing Murakumo. I recommend Shirayuki, Mandala Lord, and Kasumi Rogue. Hell, try Megacolony, OTT, Shadow Paladin (mostly witches) and Link Joker too. A lot of clans can be played defensively if you just know how to play.
Much like how Guinevere does with the name "Liberator" would be a great asset to the game itself which could get restricted to being Sentinel units much like with Perfect Guards and Quintet Walls which I feel would hurt deck consistency overall. Of course this doesn't have to be restricted to just Sub-clan names for a powerful defense since it can also be tied to a clan's mechanics as well like these card ideas for example:
Pale Moon / Dark Irregulars
[AUTO]:[Counter Blast (1)] When this unit is placed on (GC), If you have a <<Pale Moon or Dark Irregulars>> vanguard, you may pay the cost. If you do, this unit gets [Shield]+3000 for each card in your soul.
Granblue / Musketeers (Neo Nectar)
[AUTO]:[Counter Blast (1)] When this unit is placed on (GC), If you have a <<Granblue or Neo Nectar>> vanguard, you may pay the cost. If you do, this unit gets [Shield]+2000 for each Grade 1 or higher unit in your Drop Zone.
Another thing that Bushiroad should consider adding to Cardfight!! Vanguard would be defensive units that punish your opponent from restanding their Vanguard not in the same way Megacolony and Link Joker work but more so during an attack like this card idea for example:
[AUTO]:[Counter Blast (1)] When this unit is placed on (GC), If you have a <<insert Clan name here>> vanguard, you may pay the cost. If you do, choose one of your opponent's attacking units, and that unit cannot [Stand] until your opponent's next stand phase.
Those cards would all be broken, unnecessary, or both. Not to mention downright silly.