Did you decide to go ahead? Sounds like a great way to stop difficult land getting too waterlogged; mediaeval ridge and furrow was done with an eye to drainage, I understand. I have no first-hand experience of it, I'm afraid,
How broad / deep would the furrows be? a furrow between each line of trees; so a ridge and a furrow spanning -what? 14' or so? Or are you using really big rootstocks?
I think you'd have to be careful to maintain your topsoil cover throughout - so how would you go about doing it?
Perhaps you could plant some other crop in the furrows at least until the trees grow up.
I think your lawnmower might need to be four-legged or feathery...