A buddy of mine has had a couple and still has one.
He really likes driving it (and I liked it the one time I rode in it). Good power and mileage, reasonably quiet and smooth. It's a work van for him and puts on lots of high speed highway miles on the passes up here in the Rockies. Sounds like it performs great.
However, he is afraid of owning it for the long term. He had two and sold one when it went out of warranty. The one he still has is under extended warranty coverage of some kind but I think he wants to get rid of it too once that's expired. According to him there are various potential issues.... glow plugs, DEF system service/parts availability, and trans service. It has a single clutch automated manual transmission that seemed to work nicely when I rode in the van but apparently finding someone competent to work on this engine and trans is very difficult. Granted that is here in Montana where population is sparse. If you have major urban areas around you with a big dealership maybe you would have better luck.
All around though, from everything I can tell it's hard to make a good argument for the ProMaster diesel versus a far more common and robust Sprinter diesel from a similar year. Yeah the Sprinter probably would cost more upfront but in terms of keeping it going for the long term, far easier due to much greater numbers on the road, and probably less cost in the end. I'm not sure there's a single thing to recommend the ProMaster as an alternative other than possibly price.
My buddy bought two TDI-swapped Eurovans and those are his solution to moving away from the diesel ProMasters. He also bought a gas ProMaster. Apparently those have their own issues but at least parts/know-how for keeping them going are much easier to come by. The TDI Eurovans of course will be bombproof.
And your IDI Ford will probably run forever too, hard to see any ProMaster beating that on long term outcomes. If it were me I'd keep that on the road and enjoy. Those engines aren't power houses but hard to find anything more simple and tough.