Wood finishing/varnishing question

Hello everyone,
I'm rebuilding an old pop-up camper. I've used ACX plywood for the floor and cut grooves into it for a mock hardwood floor look

My questions: What's the best way to finish it: I'm planning on staining it. Then I'd like to find a finish that fills in the grooves so they don't constantly fill with dirt and grime. I was thinking of CPES and varnish combo
My problem: all the floor varnishes say they are not for exterior use and all of the exterior varnishes say they are not for floor use. It's a catch-22.
Any suggestions? Should I just use a million layers of CPES to fill in the grooves? Won't that make it have a yellowish tint (I was planning on a dark stain)? Is there a recommended product out there?
As always, thanks for your expertise
I'm rebuilding an old pop-up camper. I've used ACX plywood for the floor and cut grooves into it for a mock hardwood floor look

My questions: What's the best way to finish it: I'm planning on staining it. Then I'd like to find a finish that fills in the grooves so they don't constantly fill with dirt and grime. I was thinking of CPES and varnish combo
My problem: all the floor varnishes say they are not for exterior use and all of the exterior varnishes say they are not for floor use. It's a catch-22.
Any suggestions? Should I just use a million layers of CPES to fill in the grooves? Won't that make it have a yellowish tint (I was planning on a dark stain)? Is there a recommended product out there?
As always, thanks for your expertise