The best solution is to give up and just buy all the special cartridges (including every RTC pokemon + fresh batteries) one is interested in while they're still not too much rare/pricey.
No one will ever be able to mass produce a cost effective cartridge that covers all the different sensors, not all in one, not with an expansion port + specific module system. (said modules would cost more than the real cartridge)
No one will ever be able to mass produce a cost effective cartridge that covers all the different sensors, not all in one, not with an expansion port + specific module system. (said modules would cost more than the real cartridge)