This makes no sense. You do not want to alter the relay box so it takes nonstandard relays. Just buy the right relay already. They're about $11 each on Amazon, etc. If you live in a 3rd world country where any parts are seized by pirates and all parties executed, so this is your only option, mention that. I don't get the feeling you live on that kind of island?
If the contacts in the relay box are fouled, pull them out and see if you can clean them off (acid if necessary) and plate them (solder) for protection from oxidation, or just get a new box or contacts/harness-pigtail from a junkyard if new OEM parts are too expensive.
Do NOT alter this from standard factory wiring. There is no worse nightmare for techs servicing this and it tanks the resale value to the point of being ghetto modded trash. You'll reduce the resale value by ~20X as much as it costs to do it right.
I can appreciate that you understand it could work electrically, but it's a whole different ball game with a vehicle. Keep it standardized, with the factory config. It needs to remain the same circuit, parts (compatible, including 3rd party replacements) and layout as it came from the factory.
If it were a 30 year old vehicle worth $300 (about scrap value) then I might change my tune towards cheapest way to keep it running because it's going to a junkyard the next time there is a fault, but in your case, this vehicle has value still and that should be retained.