Would you consider getting two kittens, maybe siblings from the same litter? If you're worried about the cat being bored or lonely it would probably help a great deal to just have two, if that's something you're interested in. Personally I would recommend two boys - boys usually play the same way, and in general are more easy going and bond well with each other, as opposed to females who can sometimes be a little more independent or aloof (I know there are exceptions to this I'm just saying in my experience). If you have two, they shouldn't feel too alone or get too bored when you're away because they'll have each other. I would assume this can be especially helpful for Bengals sine they generally have so much energy and are so inquisitive, a Bengal kitten left alone on it's own for too long may be a little destructive/mischievous.
But at the same time, 6 hours only three times a week isn't really that bad. I'm sure there are also some people with full time jobs that have Bengals who do just fine.