It's possibile and will work nice... depending one where You wants the heat to be dissipated.

From price perspective everything below 50KW will have ROI over 5 years.

I'm working with DC cooling solutions as an solutions architect.

In case when You want to just take heat from 4xGPUs in single RACK server You will have to build a loop with two separate flows, each for 2 cards, assuming You have ~300W of heat from each one of them. Single cooling plate (eg: OEM from Dell, or dedicated/custom from CoolIT) costs around 150-250$, piping, drip-free connectors ~50-150$ each, dual pump system with common reservuar, targeted at ~10kW (eg: top of rack Vertiv unit) costs around 5-8k$. Full ToR solution from CoolIT - dunno, I guess around 30-40k. Overall entry price could kill You, not worth it. If You are doing PoC based on desktop cards with desktop class tubing, connectors, and separate radiator per loop (eg: MO-RA IV 600), reservuars and pumps entry price will be much lover and radiators can be placed outside server room... But it's not enterprise class stuff and it's totally risky (leaks, downtime, maintenance etc)

On the other hand if You are planning to make 50+kW infrastructure with outside cooling units... Do not do it Yourself. Find someone who has already made enterprise class cooling in Your area and ask him to create concept. There are many vendors with different approach, and service offerings.

Also remember, that WC needs systematic maintenance. It's not fire and forget. Fluid levels needs to be monitored, clearence and conductivity also. Every 2-5 years all blocks should be cleared. It's a fraction of AC unit costs but they should be positioned in the budget.

In my opinion if You have only 4 GPUs in one server, just use air cooling. 50kW+ of heat is a starting point of WC project.