wiper cowl vent delete

I didn't see why I couldn't do that , but some ppl I talked to about it were giving me a hard time saying " no you have to drill out the spots welds , pull the windshield , dash , take the whole thing apart at factory seams "

I know my car isn't a 100point show car , it probably never will be.
The rest of the body is in ok shape , the motor only has about 2000 miles on the rebuild , intereiors good....
I'm just trying to get it into shape to get it back on the road !!

I was even thinking of using fiberglass mat & resin inside the cowl area to repair the rusted out area's.
AFTER of course , removing as much rust as I can .
Figured it would be easier , no one really see's it & once it's painted should be just as durable right ?