you might wanna talk to TTL I'm pretty sure in one of his Video's he said theres medication for this.( those who want to use external wc) He'll know where to get it
but seriously looks ok if ya got the room for it. I have used external setups before. While not necessarily water only I have done an external chilled water setup where I used a medical chiller to chill water to about 10c below ambient temps. And I have used super chilled setups that ran about -45c chilled denatured alcohol as well as vapor chillers these were all done externally as there is absolutely no way to mod them inside a case. With the first mentioned setup I did however make an external case that I mounted under the rig.
Mainly saying its worth the effort to make it all self contained. I know modding is a PITA for some and in my honest opinion it is well worth the effort in doing it.
Anywho just my 2p on the matter