Limited time events...

We have events in every game. We have them in CoC as well like time decreased cost decreased for X troop. Gem bonus, XP bonus etc.

These events do not add a spice to the game.... You still have the basic troops, collectors and all, no new competitive spirit is added.
What about progression events and Raid Boss Events?

Starting with Progression events .
Progression events is much like a campaign, but with unpredictability. SC may launch a week long event, say "Mortars v/s Barbs". Here the stages will be something like -->
Destroy 5 Mortars with Barbs in Multiplayer battles.
Destroy 10 Mortars........ And so on!
This gets too easy I think. So for the weekly event, mortars inflict 2x damage to barbs.
Rewards for each stage will have increasing power like " +2 spell storage" card which can be used for one attack. The cards will have more power after every bigger stage.
Upon the event completion, a Mega-Reward like free 100% storage fill or Treasury fill can be rewarded. The event could be as large as Destroy 1000 mortars worth Barbs.
This event is just an example and CoC may introduce bigger events.. However if that defence is not unlocked by a TH level, for that people, lower defenses will be given.
Like the Top player and Top Clan leaderboard, the Event leaderboard will also be there in the Trophy menu.

A really big base will be given to a group of 10 people online. It will be like Boom Beach operations without sabotage. Damage dealt in one attack will remain constant. Rewards for attacking Raid Bosses will be -->
First Blood -- Person who attacks that base first.
MVP -- Person who inflicted the most damage.
Finisher -- Person who destroys the last building of the base.
You can attack the base several times within the time given, say 2 hours.
Attacking sequence can be like P1 P1 P1 P4, which means a single person can attack the unlimited times.. But it cannot be attacked while the base is under attacked, meaning 2 attacks can't take place at same time.
MVP will get biggest reward. Finisher (if the base gets destroyed) gets 2nd best reward. First blood gets 3rd best and other attackers get little rewards according to the damage they dealt. Time limit for each attack will be 3 minutes as normal.