Just wanna put something out there...this archetype is very meh to me. But if I played Ghostricks pre-Legacy of the Valiant, I guess I could make something work...
Shinra no Mibari Peas
This is quite cool. Shinras lack special summon capability, from what I can tell, so Peas could easily get back Lonefire Blossom to get a Plant to the field. Its normal summoning effect is meh. I'd run 3.
Shinra no Kageoushi Stool
Huh, sorta like Magical Merchant, I guess in the sense that it reveals a good portion of the deck, but only sends what you need to the Graveyard. When it's sent to the graveyard, it blows up a S/T, making it good for backrow destruction in a deck that puts your backrow at the bottom of your deck. Plus, it's got solid defense...I'd run 3.
Shinra no Mizusaki Leaf
I guess its ATK is decent...monster destruction is always nice, especially when you're doing a lot of controlled milling. Dunno how many I'd run. 2 or 3.
Shinra no Hanakishi Narsus
The level 1 reveals the same amount of cards that the level 4 does? Jeez...whatever, I think it could get some use with the effect that activates when it's milled to be able to control what you mill next. Dunno how many I'd run. Not 0, but not 3.
Shinra no Bannin Oak
Woah, now we're talking. I, for one, really like this thing. It's got good stats everywhere--level 6, 2400 ATK, Plant-type, EARTH...works with a lot of stuff, I tell ya. It can use its milling effect every turn, so Gigaplant and Lonefire love it (and even more with the former, as you can make a Rank 6 if you need to). And its effect that activates when it's milled isn't that bad either. Comboing it with Narsus could potentially put several Plants on top of your deck, then a Leaf on the tip top of the deck to mill what you just put. I'd run at least 2.
Shinra no Senju Regia
Now, this is a cool thing. Combos well with Narsus and Oak, letting you gain some real advantage. If it's in your hand, just dump it with Trade-In to get back with Gigaplant later. If it's milled, it rearranges the deck. I don't know how many I'd run (probably 1 or 2), but it's not awful! With 2 or more on the field, you could accumulate some SERIOUS card advantage.
Shinra no Morigami Arusei
And this is where I'm a bit scared...the Xyz Monster really unifies the strategy.
*Reads*
...not bad at all. Combo with Regia, Oak, or Narsus and you can basically mill or add anything you want, triggering anything you mill (But you'd need a lot of field presence, methinks...). Its other effect is a Compulse on steroids that can go off twice. I love it.
Do the Spells/Traps do anything if revealed by Shinras?
...no, of course not, that'd be too cool.
Sacred Mountain of Shinra
Still, I like. Dump dead draws or whatever works in the Graveyard and mill from there. Or, you could always use its effect during your second main phase to show your opponent what you're going to mill at the end of their next turn, thus playing mindgames. Put a Leaf on top of your deck to pressure your opponent into destroying the field spell or to not summon their big beater until they know they have game or have no fear of it being destroyed.
Blessing of Shinra
...I guess it works with the archetype, but Plants already special summon enough stuff.
All in all...I don't love them, but I don't hate them. They're not an autopilot deck by any meaning of the phrase, so you need to pay attention to EVERY SINGLE LITTLE THING IN THE DUEL. The addition and removal of 1 card from the deck could completely change the deck's strategy. I think it'll take quite a long while to create a community-accepted build.