The main problem I face is that as the PAL cases have a more than double width spine the publishers tended to put fancy graphics on the side. Converting to a standard case means I dont have much option other than to replace most with text as the small size renders the name unreadable. Saying that lots of PAL cases had text only anyway .... but purists may bemoan the changes.
Then I guess the purists can try their luck on converting them themselves

Honestly, we could use the double width spines and no one can use them (not even the purists

) or we could convert them to normal CD spines and change the little graphics on the spines to text. That way they would look like the US/JAP games which again would look good all lined up on a shelf. And as you said, a lot of games had text anyway.
I do not know the case dimensions of the PAL cases, so it would be hard for me to create covers/inserts for them.
(I am thinking of the people who have the PAL game & PAL case and just want the original artwork.)
The PAL dimensions for PS1 are:
frontcover: 123mm x 125mm (slightly bigger than a normal CD case insert)
backcover: 163mm x 122mm (with spine)
spines(s): 13mm x 122mm
PAL dimensions for DC:
frontcover: 120mm x 120mm
backcover: 151mm x 119mm (with spine)
spine: 15mm x 119mm