It wouldn't be allowed because...well, it is using the Infinity Gems in unison, no matter how you want to sell it. Having them together is what gave the gem its power, it is really all that was used.
To be clear, its the equivalent - to me - of saying that Darkseid gets to use the Anti-Life Equation because to use it, one has to "solve" it, and so really he is doing it of his own power/intelligence.
But Thanos created a weapon without using the gems power for what they are designed for. It isnt like he is messing wit reality or time but he used them as a power source to create a weapon capable of destroying the universe. Fine I thought it was allowed but if you want to argue against it I really dont feel I needed it anyways.