In my theoretical example it actually will shrink it by a couple percent… but in your situation, yes the whole model would grow a bit.
Unfortunately I can’t think of a good way to do what you’re asking without some serious manual adjustment. There are some faster workflows for this but they all will require some manual work.
The ultimate solution would be to import it into a truly parametric app like F360, done correctly it would allow you to resize your slots more or less at will. A similar result could be had using inkscape/AI and clever use of clones, but you’d have to tread carefully.