That's cool.
I don't know I think they would just have to re tool Battle Grid mode like make it some Holodeck, Danger Room type thing.
That or, and this may sound weird just save it for when the Ultra Skugs are introduced as a power up to deal with the Ultra Skugs ala the Ninja Rangers from season 3.
As for mecha that's a good question this may sound weird but I always wanted to see something where the Troopers have their own individual vehicles that combine into a robot.
A robot that's already a robot to begin with, and doesn't transform
And finally a robot that starts off as a carrier spaceship that transforms into a robot,
And their version of the Ultrazord is their individual vehicles form their robot which then docks into the second robot, which then docks into the third robot.
I think a good example would be the spaceships, and robots from
Macron 1/Goshogun, and the spaceships, and robots from
SHSSS/Gridman.
As for who would play Grimlord I don't know I always thought Clancy Brown would make a good Grimlord