Nissan's Urvan vans have been popular vehicles for DIY campervan conversions for years. Mainly due to their long length. But these vans are also popular with carpet fitters, again for their long length, and there aren't many to be found today.
However, Nissan make great new vans and you can find lots of professional conversions. The Primastar, Serena and Elgrand vehicles make great weekend campers/mpvs.