I have made gin with and without grains of paradise and honestly I don't see why we are making the effort to source this fairly obscure ingredient that is difficult to get hold off and it's easy to substitute. I think because it is used on the original Bombay Sapphire gin it became "desirable" to use and found itself in many gin recipes but in reality you can just use more pepper, Szechuan pepper, coriander and other botanicals as a substitute and still produce a great gin and you can also produce a gin that is just like Bombay without it too if that is what you are trying to achieve.
My opinion is that I really would not bother and stick to more botanicals that are easy to source and Australian grown where possible.