I quite understand, FE is a bit rough, but it suited a cottage for that reason. I like Nigel's idea of shiplap (or matching would work for the same reason) because its way posher. Are you planning to paint it or keep it au naturel?
Just a coat of preservative Bob. Probably the new 'creosote'. Or maybe Cuprinol.
I think ship-lap looks best when fixed horizontally. And that looks funny on a gate. Or is it just me?
If I do come down in favour of decking strip, I might machine a generous rebate and make it into ship-lap.
I made one from close boarded oak pieces on an oak ledge frame - still going strong after 38yrs. Very heavy though and supported on large strap hinges (if that's the correct term?).