"unconventional decision" is correct and usable in written English.
You can use it when referring to a decision that may not be typical or expected in a given situation. For example, "The team was surprised when their coach made the unconventional decision to switch out their top scorer right before the final whistle."
To refine the content of the memorial, Gehry made a typically unconventional decision.
Shug McGaughey, a Hall of Fame trainer, made the unconventional decision to train him for the Travers after starting him in every Triple Crown race.
Central Office strategists made the unconventional decision months ago to launch the Tory manifesto within two days of Blair declaring the election.
Art often works this way, serendipitously: it announces itself in the nuance of an unconventional decision, suggesting the spark of sudden inspiration.
So their manager, Davey Johnson, made the unconventional decision to let his players skip practice on their day off, allowing them to sleep late, see friends and family, and avoid the scrutiny of the news media.
After their second tie against the Czech Republic was out of reach, the two Minnesota-born Americans made the unconventional decision to have Mattek-Sands serve first in the largely meaningless dead mixed doubles rubber.
They know he carved his Hall of Fame career from unconventional decisions made in haste.
But Belichick, who has long embraced different approaches to managing a game, makes plenty of unconventional decisions, one reason he is widely regarded as the best tactician in the game.
"Travel light" is the greatest lesson I've ever learned; executives in developing nations must consistently challenge themselves to not let accepted business practices prevent them from making unconventional decisions.
The seventh stream of research was suggested by March himself (1976), who linked the technology of foolishness to the ability to re-interpret history, creating a coherent narrative that, at the cost of distorting the past, enables novel, unconventional decisions to be made in the present.
Everyday, single mothers across the country are forced to make unconventional decisions because of societal structures in place that make it almost impossible for a single mother to thrive.
