Certainly a possible driver move that didn't happen: Jari Nurminen to Arrows or Coloni, 1987/88. He was the test driver for Arrows in 1986, while competing in F3000. He later achieved some success at WSC. Snippets from a 2014 interview at F1-areena.fi:
Q: How much did it affect your career when you couldn't get top equipment in F3000?
A: Everything depended on that. It was all purely due to money. I had to drive with 25% of the budget when compared to Capelli, Pirro, Moreno, Gugelmin, Lehto, Alesi, Bernad, Danielsson, Herbert, Cauchon, Tarquini, Weidler, Campos... and so on. We couldn't buy the best engines or test more than 10% of what these top drivers tested. We did test - whether the speed was due to me or the equipment. For example in 1986 at Monza Ivan Capelli tested with me. He won the F3000 championship that year and later drove for Ferrari in F1. I was 0.6 seconds faster than him on that day, even though we took turns for the entire day behind the wheel. Both maybe 60 laps, so it was not just 2-lap qualifying runs. The series was just so tough during those days that there was no chance without being in a top team with high-end equipment. There were over 50 cars enter, with at best a dozen F3 champions. I was twice fastest in practice and if I remember correctly, my best race finish was 7th. I believe that with better equipment, I could've won just like the others did.
Q: How did it feel to test the Arrows F1 car for the first time?
A: The power was great, but I was surprised at how easy it was to drive. F1 car was a lot easier and steadier than the F3000. You really had to drive fast and on the limit the entire time with an F3000, whereas you couldn't do that with a turbocharged F1 - you had to "wait" in the corners instead. On the straight however, the pace was quite different. We had 1200bhp at best, so it didn't really matter which gear you were on, the car was flying.
Q: Why didn't you get an F1 drive in the end?
A: Only reason was AKK (Finnish motorsport federation). I had a signed contract with both Arrows, and next year with Coloni, but both years AKK turned down my superlicense opportunity. I also had the funding that those contracts required. Arrows liked my testing efforts while Coloni knew me from my F3000 days and was there, when I beat Capelli at Monza and held me in high regard because of that. Capelli was back then regarded as Italy's #1 formula/open-wheeler driver.
So: Nurminen was supposed to drive for either Arrows (presumably in 1987) or Coloni (1988). Shot down due to AKK being idiots. Personal note: In Finnish, Jari comes across as not very humble, but also very honest. But it's also a period-piece of interesting information, especially regarding both Arrows and Coloni being highly interested in Nurminen's services. I'm also rather curious about his funding; didn't get much in F3000 days, but later on had secure financing for an F1 drive? That's interesting. Not saying there's anything shady, it's just interesting. Finnish drivers, as I assume is the case with a lot of drivers around the world, don't really get sponsorship easily unless they already have proven themselves at a rather high level.
As a translator's note, some of the sentences were written in a fashion that was rather unorthodox. Not wrong, just different phrasing and punctuation that one would see in a professional publication or even what I'd use. However, since this is an interview, I tried to use similar phrases and keep the text true to the feel of the original. Not sure how well I did in that, but I tried.