I run a LWB hi Roof transit. 04 plate. yes transits rust, but you can find decent examples of them around, if you spend the time looking. A little bit of rust can be repaired, and transit parts are cheap and easily available. engines are easy to work on too. With a bit of care you can get a transit to do very high miles with low cost. The load capacity of a transit is good, the space is good.
As for towing, get a RWD van. Also, the diff ratios matter when your towing, hence why all RAC and AA vans have different ratiod diffs. My van had a ratio set for towing, pulls the trailer well, cant even feel it but when im not towing the trailer, it revs a bit high on the motorway. small price to pay for having a good all round van.