It's very hard to think of the power of throne, scheme and similar cards abstractly, but let's try.
Sometimes I think of Throne room as a kind of Village.
You can have a Village chain, it will allow you to play one additional terminal per Village.
The "play it twice" of throne room is like "+1 Action, phantom +1 Card +1 Action" with a duplication effect. "Duplication" means, hey, I have another copy of this Action on top of my deck (there are differences in the duplication effect of TR and Scheme, TR only copies the Action while Scheme copies the Action card).
You can have a TR chain, it will allow you to play one terminal twice per TR.
Now, Scheme is not a Village at all, it is just "+1 Card +1 Action" and the Action card duplication effect (for your next turn).
You can have a Scheme chain, but it won't let you play additional terminals, it is just for the duplication. It can also duplicate itself.
Simplified, it is like:
$3 Cantrip +1 Action (Village)
$4 Cantrip +1 Action +Duplication (Throne Room)
$3 Cantrip +Duplication (Scheme)
What is Flagship?
On current turn, it is just +1 Action. On the next turn, it is +Duplication, phantom +1 Card +1 Action.
In theory, it is the same thing that Throne room does, just with a delay (similarly to Lab -> Caravan).
Silverspawn emphasizes the Village effect on the next turn. Yes, it is strong, especially with carddraw.
The problem is, Flagship is not really a Village because there is no Flagship chain: Without extra Actions you can Flagship at most 1 Flagship.
For most of the time, my Flagship did cost $4. It was a bit of an experiment to post it here at $2.
With +1 Card, I think it would be very comfortable to play. Maybe it should cost $5 then.
