I think the easiest way to make the gatcha fair and fun for all would be the following:
Keep the current % or possibly make 6* 1% instead of .5 but when someone rolls a 10+1 roll make that +1 a 5* every time. Sure you loose 1 chance at a 6* but at the same time you get some real value from each pull and you will never really feel like the 50 gems were wasted (unless you get a dupe that you have had 10 times before, but it should be rare still).