Ya, it’d be doable for sure with the craze of all the overland van-dweller builds the last few years. Ive seen plenty that meet all your requirements. But, whether it would be cost-effective or not for a work van would be the major issue, especially considering most trucks can do all that without being a special order for probably less than half the price.
Unfortunately not a lot of demand for such a thing, like you said.
Years ago i was in a spot where i needed the same as you for basically all the same reasons. The old van kept getting stuck everywhere, and then it actually got rolled from hitting a patch of black ice one winter, so it was totaled. These high-top vans had just started coming to market which was great, but I couldn’t convince the boss to spend the extra money for at least an AWD version, nevermind the higher ground clearance or low-torque options. I still got that thing stuck so many times…having a high-top I could stand up in was nice though.