I'm not a fan of the AC unit being in the attic because it's usually hard to get to it. The other issue is getting to it without clearing a trail through the insulation every time you change the filters.
I have 6 large dogs, and I change my filter twice a month in Summer when it's dusty out, and once a month the rest of the year. I also add bleach to my drain every time I change my filter. I had them double my filter to 2 inches thick because of the dog hair that ends up in there and the hair would clog up the filter and bend it.
I've built bridges for clients to get to their AC units when they decided to have their Insulation redone. Most of my clients are too old to get into their attics to change their filters, so it doesn't get done, or they pay somebody to do it.
Be sure to have a walkway, or bridge, to get to the AC Unit so you can do basic maintenance and not ruin your insulation.