The only issue with letting water into the dry side is that the soil will move down into the gravel and then may start to leaching into the water. Also, the water will most likely seep up into the soil and then it can become quite soggy and putrid quickly. I had one where water leaked into the dry side and it was awful.
You could use a small undergravel filter on the wet side (of course well covering it with a number of inches of heavy gravel to prevent them finding a way under it, or a powerhead to circulate water. Another kind of filter that can work quite well in these set-ups is like this one:
HerpSupplies.com - Turtle Clean 511, Canister Filter - Zoo Med - TURTLE CLEAN 511 CANISTER FILTER- ZooMed External canister filter...
It has a straight uptake tube attached to aquarium tubing that leads to the external filter and then the water goes back to the tank through some more tubing to a long rigid piece with holes in it. You can choose to place this above the water allowing fine water spouts to hit the water, or under the water, which creates some movement of the water without any splashing (which newts don't enjoy too much if it splashes into their faces).
Therefore only the small intake tube and output tubing is in the tank. The only issue is making sure that the lid is adapted to prevent any extra spaces for the newts to escape.
The dry side can be decorated with plants and moss. The moss can be misted to keep that side slightly moist, but the Tylototriton spp. don't need to be kept very wet.
I have known T. shanjing to dwell a lot in the water, and then they choose to spend more time in the dry side. I have heard some rarely use water, so choices are good.
You could always but a small, shallow water dish with soaked moss in it on a part of the dry side if you want to give them an intermediate.
Hope this helps.
Rachel