there's been a somewhat similar discussion about night vision... I think it would be nice if all of this would be moved to the ruleset, including the possibility for items to change this.
in my mind, the perfect openxcom would have
- sight range in the ruleset
- sight range modification via use of items (using binoculars gives a soldier an increased sight range until he moves or takes another action, for example)
- a "minimum light level for vision" defined in the ruleset: each unit can only detect other units sufficiently well-lit.
- "minimum light level for vision" modification via item use (advanced armor types have night-vision installed; night-vision goggles like binoculars above)
some aliens would perhaps have a rather shorter vision (silacoids?), others could see quite far (mutons?), still others would have supreme night vision (sectoids, chryssalids). humans would have average sight range, and mediocre night vision