I don't remember having trouble with removal on my MK1 Rabbit. Seems like the blower came out with a bit of twisting of it down on the end of the bay by the hinge. Tight fit yes, but nothing more. What is the purpose of the flashing? Wind blowing in or stuff in the blower motor?
I think that pic shows the fresh intake for the AC version. Notice the vacuum dashpot...I presume yours is non-AC?
I think I would have gone for screens on the ends of the blower motor, maybe with changeable filters?
Too bad… I just sold a NOS Non-AC leaf basket that covers your blower motor. Though you definitely have gone to the Nth degree to accomplish your goal.