In my country, the dobes are used as watchdogs for the house and most are left outdoors and most of them don't have a problem with scratching. it's only minei have the same problem here in the summer. i still wouldn't bathe my dog that often. i'd have a kiddie pool for her when she's outside but we have air conditioning for a reason...she does not stay outside all day long.
i would reconsider your "outside only" plan. this breed is not meant for that.