Remove the instrument cluster and it will be much easier to get at the two screws on the back of the ignition switch. A mirror and good light will help you see what you're doing through the rats nest of wires. Be careful not to drop the screws and turn it into a treasure hunt (why do I know this), so remove the under dash panel just in case. With any luck you won't need to go upside down under the dash with the blood rushing to your head, although I've sometimes decided to do this for a moment just to get the lower screw started and do the final tightening when too many wires are in the way from above. A double ended offset [Z] slot screwdriver can be of help, especially with the lower screw.

Note that yours is the early switch p/n 9203247, which is no longer available in the Volvo parts chain. You may find genuine Volvo ones on eBay in old stock. The only identified aftermarket switch I see available at the moment is the one distributed under the MTC name, apparently made by Ronak. MTC is often listed as OEM (meaning OEM quality), rather than the OE supplier. IPD sells it, plus it's currently available on Amazon for quite a bit less.

Your thought about wanting to use a bunch of separate switches to avoid the chore of installing a new ignition switch gave me a chuckle. I had visions of a row of toggle switches in the dash. Like a space rocket launch you'd call out to the passengers, "Systems On!", "Ignition On!", "Firing the Rockets!", "We have Ignition!", "Ready for Liftoff!"
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now