I always think its more fun if storm shield can also force a contest

Like 1 storm shield, the team fights for it.

Or even remove storm shield, put a dragon there with gold for everyone and a buff for the whole team (balanced by a much weaker buff for 5 instead of a strong buff for 1)

Buffing one person can already turn a fight. Why would you want to buff the entire enemy team? So they can 5cap with no problem? No thanks.

its already a contest sometimes, if both teams know that they are trying to get their respective buffs. riot also wanted to maintain a difference between the maps and not have a "dragon" or "baron" on the map.

As Hamm3rhand said, it can already be a contest. Trying to take the Storm Shield might put you in an awkward position, and it should therefore mostly be done when you know where the enemy team is, or when you have some good escapes or people protecting you.

Yeah, there are skirmishes over storm buff all the time.
I've seen a lot of Ez ults used just to stop one person from getting it.

When i play assassins, i will hover around mid if the enemy storm buff is up. Someone is generally going to want it, then i blow them up and prance away(or sometimes die horribly lol).

I think the map would be better if there were only one stormshield.

I actually like this idea. Not necessarily the dragon idea, but some kind of contested buff in the center. Maybe to replace the windmill being set as a quest point(because that always drives me nuts). So perhaps there's the four side-capture-point quests, and then a center buff/gold goal of some sort that can be contested. It creates nice tension, especially being stuck in the middle of a whole bunch of fog-of-war like that. Also could provide a choice for teams as to whether to go for the buff, or get a quick cap in while the other team goes for it.

Alternatively: rather than offering an offensively-oriented buff(gold and/or combat boosts), it could be a defensively-oriented buff instead. Like maybe a long-duration garrison on the towers on your side that you control, or maybe a set of cap-interrupting turrets(like heimer turrets) on points that you control that need to be destroyed before a team can cap.

i prefer the defensive part of things everyone knows that although killing is important in Dominion,, rampant bloodcrazing is just detrimental to your play and loses more games that it wins many people would try to misuse it for rampant turrent capping feeding the enemy team a lot of gold or what you know happens with baron at low ELo play, Team A gets BAron, Team A says we get baron we win, Team A doesn't even recalls and goes balls deep into enemy siege, Team B Aces them and wins match or at least takes baron away from them which turns into a wasted BAron.