As with the previous comments, I think this is a very cool idea. As ket put it, "fresh"!
"Fresh!" 
I am particularly fond of the idea of having Serie 4 be Pre-Shadows Multipath.
Pre-Shadows means more freedom. After playing each film's sites once, don't see a reason to force the King sites to be played again. Many players (#metoo) will learn from this experience some of the potential of good ole Pre-Shadows Multipath.
I'm still of a mind that Ulaire Nertea, MoDG is better left to the booster luck...
Nertea MoDG would singlehandedly erase the lame Towers sealed Ent Swarm, think about it!

His presence is a big warning to companion dumping, which becomes too easy in the 2nd half of any Sealed. Perhaps 2x is too much, but appearing in Serie 4 along with 3x Reflections boosters should balance each other I think.
Tower Troll is a great suggestion by Dictionary, 1x plus 1x
Nertea MoDG can be better than 2x Nertea. What do you think?
Dictionary's comment did make me stop and think... there are a lot of rares that wouldn't grossly disrupt the balance of the sealed if included, hence it might just be "overrated" (as in, it's a habit) that we exclude rares.
Tower Troll has the same chances of being pulled in boosters as, say,
Steward's Heir (P) or
Thrarin SoE: zero. Rare and Common are the same in case of being an outsider card. And actually, rare means nothing for
The Weight of A Legacy too... it's all about power.
UTWE is much more powerful than
Seeking Its Master, and that (in a good strategy) is what gives players victory or defeat.
The only counterproductive aspect I see in including moderate rares is diluting the value of rare pulls. So 1x should be ok as you suggest for each "Evil Guy pack."

I thought it might be interesting to give the player a choice for which "evil guy" they wanted to go with. As in there are, say, three key minions each block, and they choose one based on what direction they want to go with from their booster pulls and starter deck.
I like that idea A TON! I started with 4 cards but we could make them contain a bit more, say 5 or 6 Shadow cards + 1 favorable site (like
City of the Dead for Shelob, or
Deeping Wall for Saruman) to make them more versatile and impactful, while making some villains much easier to include (Saruman needs combos, Nazguls need numbers, Isen Men need conditions).
That solves 2 common problems of Sealed leagues:
1) When your basic Shadow side simply cannot bite your opponent due to a key pull (like
Ranger's Sword or
Gandalf FotS in FOTR sealed, Uruks without pumps don't make it), you have no choice but to
try to outrun him/her. This addition guarantees Shadow decks will have a minimum biting power, much higher than what the basic starter decks have (and that also removes a lot of pressure from choosing Boromir or RotEL Legolas, knowing their Shadow sides usually suck).
2) Great pulls that depend on other cards... that you didn't get. Like several copies of
Desertion, with few if any
![Isengard [Isengard]](https://lotrtcgdb.com/forums/Smileys/classic/isengard.png)
Men.
------
3 Evil Guys per block. Let's start with FOTR Block, these are my ideas by now:
1. Twilight Nazgul pack: (6 Shadow + 1 site) - 1x
The Witch-king LotN (rare)
- 2x
Enquea, RiT- 1x
Otsea LoM- 2x
Fell Beast (outsider)
- Site:
Ford of Bruinen2. Balrog pack: (6 Shadow + 1 site) - 1x
The Balrog, TToKD (rare, outsider). Non-underground Balrog, which means he'll still be useful after Serie 1.
- 1x
The Balrog, Durin's Bane (or
Goblin Spear, if each player gets 1x
Durin's Bane outside the Evil Guy packs)
- 2x
Dark Places - 1x
Power and Terror- 1x
Foul Things- Site:
Emyn Muil*. Fierce balrog above the ground. (only Gandalf set 1 and Boromir pack it)
3. Saruman FOTR pack: (6 Shadow + 1 site) - 1x
Saruman's Staff (rare, outsider). Fighting, fierce, self-assigning Saruman means trouble.
- 3x
Saruman SotE- 2x
Isengard Smith, or
OOYMDT- Site:
HollinThe addition of key outsider/rare cards will provide a new experience to all players. "Fresh," one might say!
Each of these packs will benefit better one or more Starters: Saruman will charge Legolas and Aragorn, the Balrog will enhance both Gandalfs. Gimli's Shadow seems to need no help (being Grind, would benefit from the Twilight one better). Boromir's Mordor Orcs might find some relief from their
uselessness high roaming and clogging factors in the Twilight Nazguls (
Fell Beast ftw!), but still might be insufficient.

Any objection or suggestions? It's a prototype by now.
Altogether, I think this would be a lot of fun!
Thank you for proposing it!
It's the least I can do to save fellow players from cutting their wrists in these dark times!

Thanks dmaz for your feedback!