Car looks fantastic! It's a great colour for a 740, and the wheels are classic 80s. Love it!
+1 for not bypassing the relay with a switch. Also fairly sure it wouldn't be legal (for a good reason).
The way the wiring for the fuel pump works (and the fact that you want it to still be protected by a fuse) it's probably actually easier to replace the relay with another one than it is to replace it with a switch, as well as being much safer for yourself and your components.
If you want the new relay to last essentially forever, you can use a $10 Narva relay to take the current load off the (more expensive and complex) fuel pump relay - I have done this, and it's a very robust approach. Details here, about 3/4 of the way down the page:
http://www.davebarton.com/volvo240mods.html#relaymods (instructions for 240, but it's the same relay, so can do the same process on 740).
