The Mess? What mess? If you do Istinja properly there is of course no mess.........
And Istinja is absolutely necessary. Definitely. A Muslim has to cleanse himself properly whenever he leaves the bathroom. If water is not available then tissue can be used.....However they should be used an odd number of times. For example not two wipes, but 3 etc.
But even though it's permissable to use tissue etc. this should only be resorted to if there's no water available.
Rasulullah was once passing by two graves and he said to his companions " Verily the inhabitants of these graves are being tortured, and they are not being tortured for Major [things] as for one of them, he did not used to cleanse himself properly from his urine......"
Perhaps you should find a vessel more suitable for it, because it's definitely not messy.