I recently did this with some difficulty. The Inspiron 530 case has no cut out for the motherboard face plate. I used a pair of tin snips to cut a rectangular hole to fit the new face plate. It is a little crude, but I managed by sheer luck to line it up correctly.
The other minor issue is the front panel connector. You have to remove the wires from the connecter, trace them back to the power button and LEDs and connect them properly to your new motherboard's front panel header.
Otherwise, the case has the proper holes for mounting a micro ATX board. I installed an ASRock Z68 board which has been working great.
Why is it that you want to be able to upgrade the motherboard in this computer to something else?
DELL has a long history of trying to re-engineer their parts so they are maximally useless with anyone else's parts, obviously so they can lock people into buying upgrades through DELL rather than companies that are forced to compete with each other.
Since I have freed myself from DELL, I haven't been sorry. I would get a new motherboard and a new low end case to go with it. You can get an entry level case starting from about $20 shipped.
I can't speak for the OP, but the Inspiron 530 case is actually a nice small and light case that is uncluttered inside. I wanted to keep mine.
As far as your other comments, none of them apply in this particular case. The Inspiron 530 uses a standard micro ATX motherboard, standard PSU (with standard power connector) and standard everything else as far as I can tell. There is no reason to buy upgrades from Dell. The only real issue here is that the motherboard I/O back plate is built into the case.
But after having messed with altering the case to install a different motherboard, I agree that the best idea is to just buy a new cheap case.