I'd rather simply make it not possible to go back to the BUY position once you passed it: if you make a very high bid, you can retreat only at the lowest price, but never back to the $0 bid.
This means when someone makes a bid he IS going to "battle" for the possession of the land, but can't withdraw entirely from the "battle".
OK, here's an interesting problem with that.
Let's say 3 of our players get involved in the 'run the price up' game. Or worse, three people bid... but then two run it way up to North Craziland.
Then they all run back down to the 'buy' line, including the poor sucker who stayed down there, as prices went way, way past their ability to buy.
... who buys it? At what price?
The person lowest in the rankings? What if they don't WANT it at this crazy price they couldn't control... and can't even afford it?
The person highest in the rankings? Sure would be easy for a lower-ranked person to force a sale at an insane price, that would screw everyone.
The person who was the last to come down? What if one of the others got the 'jump' on them, on the way down?
The one with the highest bid, ever during the process? I suppose that's the least prone to awful.