bear in mind that either way you need to be able to radiate the same amount of heat if you want to maintain low inlet air temperatures, so you will still need a biggish pre-rad for the charge cooler water, otherwise the water will just get heated up and the efficiency of the chargecooler will drop away and inlet air temperatures will rise.
Chargecoolers are OK for short-term cooling whilst the water is cool, but under sustained boost the overall heat dissipation needs to be the same as for the intercooler, so you need a means of dissipating the heat from the charge coolant.. and a little pre-rad squeeezed in wherever isn't going to do it.