I would think that it is appropriate to "stand on the shoulders of giants" and take the lead from your favorite manufacturer who has already put in the time and effort (R&D if you please) to find some good solutions and compromises regarding scale, response and tone.
So I would find a good example of a Wheatstone, Lachenal, Jeffries etc whose tone and response are preferred and which has reeds that appear to retain their original profiles.
Also check the scale (varying lengths) of the reed assemblies to make sure they are compatible with your project. You would then use a micrometer to take measurements of the tongue out of the reed shoe in at least 5 places and more, if patience and persistence exist. This will give you the profile of a reed tongue for that particular note. Often notes a half step above and a half step below have the same basic profile prior to tuning.
If you haven't viewed the Pathe film, "Concertina Factory", which has snippets of the Wheatstone plant, you might find it beneficial. In the Wheatstone factory, and I would guess many other concertina operations, a plate of spring steel was give a particular profile using a surface grinding machine. They are usually water cooled which preserves the steel's temper. The profiled plate was then sheered into strips which eventually become the reed tongues.
I believe a number of the modern manufacturers of concertina reeds began with this process of imitation and then develop their own variations according to their likes and needs. It is a time consuming process and can make one appreciate all the work that goes into making a good sounding concertina.