Whilst I support the idea of a test/first class promotion system I have found that every proposal so far raised to be poorly designed, unfair (and that's ignoring the complete disgrace of three teams being exempt from relegation).
So I've developed a system on my own. This covers the 48 ranked teams (the top 12 have test status) over 8 divisions. The top 20 teams have ODI and T2OI status. The status of a match is determined by the status of the team with the lower status (eg Ireland vs Netherlands is a first class match but Ireland vs Bangladesh is a test match)
Test matches last for 5 days and first class matches last for four days. However for pro/rel points there is no difference between a test or a first match.