The majority of the skirmish games that I play do not define facing for individual figures. The exception (and an important one for me) is in the rules for Two Hour Wargames (THW) skirmish games. Since other games I play do not use facing, I do not get used to it and maintaining figure facing during play becomes distracting to me.
So after some consideration I decided to adopt the following house rule: figures do not have facing. When an active PEF comes into sight of my figures and resolves as a number of enemies, I roll 2d6. If the result is 11 or 12, my figures have been surprised, so they suffer -1d6 in the In Sight test, while the enemy does not suffer the usual -1d6 for being active. The same applies in reverse if my figures, while active, become in sight of a PEF. This "surprise check" is not used when actual enemy figures (not PEFs) are involved.
My rationale for this house rule is that, given the level of detail of THW games like Chain Reaction or After the Horsemen, I feel that the usual hypothesis for other skirmish games -- that figures are not static but rather, looking around and shifting around their marked position -- is also valid for them. Besides, figure Rep and line of sight will already interfere on any In Sight check. The "surprise check" just adds a bit of uncertainty to it all.