Enclosure openings are a matter of personal taste & experience for what you're comfortable with. I've used sliding doors & yes, they have their problems, but for an aggressive feeder, you can also open very slightly to offer prey to the snake inside, without being a big target yourself. Honestly I prefer top opening tanks, but that's me, lol. And yes, that was even for the big snakes including the BCI I used to have (she was 7.5- nearly 8').
Quarantine also means being mindful that YOU are also a "vector of disease"- ie. able to transfer pathogens on your unwashed hands & clothing between your snakes. And NEVER re-offer food between snakes when one has made contact but decides not to eat. This comes under the heading of "good overall practices"-
And mites are also a vector of disease- so make SURE there are none while the new snake is quarantined. It takes time for mite eggs to hatch.
And not to be paranoid, but remember that some diseases can "hide" in boas for far longer than pythons- where the boa is an asymptomatic carrier that may never even become ill, or at least not for a much longer time, but which could decimate other more sensitive species (pythons). So the length of your boa quarantine may depend on how you feel about any pythons you already have.