I have played other games that different categories of boost; Building, Troop training, Troop Healing and Research. As you concentrate on one section of the game, you can accumulate boosts in other areas. It could then be possible to accelerate other areas. 

Or is the limitation created by the single boosts necessary to the flow of the game as intended?

In Stormfall the boosts are universal so they can be used fortroop building, building time reduction, or recalling troops more quickly. Only the time reduction for sendingtroops on raids or sieges is separate. With the addition of Building help, the need for universal boosts was reduced slightly.

Most other games have some type of alliance help, so the building help is catching up with them. Urgent help although is something i haven't seen in other games.

Urgent help although is something i haven't seen in other games.

So, do you like it? :)