Which name?

So me and my partner have decided on the name Ethan but we also would like to honour our grandads names William & Arthur so his name was going to be Ethan William Arthur but I also would like to have my dads name Ian somewhere in this I'm unsure wether to remove William & have Ian instead? As William aka (Bill) wasn't my actual grandad just someone I cared about dearly and looked up to as a grandad what shall I do?