Make middle a capture point instead of 2 seperate buffs, you can capture it just like the other towers across the map but it doesn't fight back if you stand around it. It would take a single person around 15 seconds to capture from neutral, each additional person channeling would reduce time needed by a little bit. Capturing gives everyone on your team the buff but make it slightly weaker than it is now in terms of how powerful the shield is and how much damage the attack is, maybe make it recharge a tiny bit faster.

The tower would become first activatable at 3 or 5 minutes into the game, so it's not just everyone rushes there right from the start.
The buff would be changed to persist through death, and you could tell how long is left on it because the middle tower slowly ticks down until it's neutral again. Once the point is captured, it can't be captured by the other team until its duration runs down and it becomes neutral again, that way not everyone is always middle all the time either.

I think this would encourage more teams to want to go mid and really want to keep control of that buff, right now it's just whoever gets it gets it whenever they want to walk by it.

This is a very intriguing idea. I kinda like the premise of having a second quest that you can go for, which forces teams to make a decision of either going for more points or going for a temporary buff. In the premade team matches, you often see the middle buffs go untaken for long periods of time simply because the time can be better spent elsewhere on the map, and the buff isn't THAT useful compared to actually attacking/defending a point. A change like this would flip that on its head and make matches more interesting for high elo players, even though it may just confuse lower elo players a bit more. Unfortunately, I feel like this would take a ton of balancing and playtesting (at least, for Riot it would XP), and I would rather see Riot finalize Dominion as a game mode so that they can get ranked out for it.

Making it a weaker team buff would improve it's usefulness and make it a real objective, instead of something you go for because there's nothing else to do.

They would really have to weaken the shield on what the buff is now and remove the lightning procs completely in order for it to still be balanced during that time. I would like this put in though and maybe include the 10% damage buff from quests with the shield.