Appreciate what you're saying, Sue, but I wouldn't put ANY bull in a field with a public right of way whether dairy, beef or dual purpose. Just as I have never put newly calved cows anywhere with a public right of way. To me, that is common sense. Don't put animals where they feel threatened or under stress and don't put people in danger.
ALL bulls can get knacky. All bulls must be treated with respect and understanding. The gentlest of bullocks can turn into a right old bugger once he's mature and within scent of females. The one thing I would say as regards my choice is, unlike commercially bred Holsteins, Guernseys are renowned for their docility. Before I get messages saying "My Holstein's a pussycat" or "I knew a Guernsey who listened to Megadeath, smoked crack and held up my grandmother for her pension", let me just say that, yes, there are good'uns and bad'uns of every breed. This is, all of that being said, a cross I would like to try.
You have a short window of viability, especially in bad weather. A cow's fertile period can be as short a 4 hours in weather like this, and if that happens in the middle of the night, you've missed it. A bull is less likely to.