Testing, deploying, and supporting new software costs money. There's no way around it and it's not directly related to the expense of the software licenses required.
This could be possible with Firefox too(I don't know), but I would require a specific tool to be developed, tested (by Mozilla for example) and LEARNED by the admins.
The tool itself needs to be deployed...
First result for "Group policy Firefox"
Plus the cost of training IT people to install Firefox across thousands of computers (you didn't think they'd install it one-by-one did you?).
Etc, etc.