Working on a number of "gateway" challenges for a client. Not sure if this is too hard with zero hints. It's so hard to measure when you're the one who create

Working on a number of "gateway" challenges for a client. Not sure if this is too hard with zero hints. It's so hard to measure when you're the one who created the puzzle. I came up with a couple solutions but again how do you separate the personal bias of being the puzzle maker?