on my "91 Volkswagen Vanagon GL Campmobile 2.1 waterboxer.

It occurred to me that if the oil cooler works well, the oil might run too cool when ambient temperatures are relatively low.  Is it possible (and practical, reasonable) to install a valve in the feed line for the cooler (and maybe another in the return line) that could be opened and closed depending on need?  I realize that this would create an additional complication -- that it would be another point for possible failure.  Or am I just trying to over engineer something?  Anyone with experience with an auxiliary oil cooler might know if I am trying to solve a problem that doesn't exist.  Maybe the oil would have no problem running hot enough, even with the extra cooling capacity.
Thanks, DMc
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David McNeely