Good idea for sure! Might have to look into maybe cutting that open and cutting out a brick and mortar and add your own drain maybe put a little bit of a gutter along the back with a little downspout? Not sure if it's in the budget but it would definitely fix your issues. You can prime and then...
I suggest you clear that water off, clean off from the bottom of the black rubber on the wall up the flashing and up the brick. Seal from the bottom of the wall all the way up to the top of the inside of the wall with a liquid urethane. Not sure of the liquid applied systems you guys have but...
You will also want to pull some of the insulation back from your attic. Pull it back from above the soffit sometimes it clogs up your soffit holes and doesn't let it breath like it should. It is a common problem here in US. Have a blessed day. Give it a shot before you change your fan.