So what i was thinking is to create a enclosed room in garage or use a grow tent and cool that room and have the air flow intake of the miners air flow coming from the Air Conditioned enclosure via flexible air duct pipes?
Can it work? Of course it can!
But you haven't told us how much heat you're making there, you have 4 S9 or 30 S19 there, when you say summer is that 30C or 45C outside?
The thing is that in extreme situations you might have to spend( depending on the electricity price) too much of a percentage on cooling, so maybe just doubling the air flow would be a cheaper and just as effective solution.
And the machine numbers and their watts will also give a clue on the tent/room solution, I personally would always feel on edge knowing there are 25kw running in a 2 cubic meter oversized pot bag.