What is the maximum voltage you can have on exposed rails?
690.31(A) nixes your diabolical plan

Unfortunately, unless you could find a racking system specifically listed to connect the contained panels in parallel as you describe, you can't do what you're after, as 690.31(A) requires a Chapter 3 wiring method, or a wiring method explicitly listed for use with PV panels, for all PV system wiring:


  690.31 Methods Permitted.
  
  (A) Wiring Systems. All raceway and cable wiring methods
  included in this Code, other wiring systems and fittings specifically listed for use on PV arrays, and wiring as part of a listed
  system shall be permitted. Where wiring devices with integral
  enclosures are used, sufficient length of cable shall be provided
  to facilitate replacement.
  
  (1) Identification. PV system circuit conductors shall be identified at all accessible points of termination, connection, and
  splices.
  
  Where PV source and output circuits operating at voltages
  greater than 30 volts are installed in readily accessible locations, circuit conductors shall be guarded or installed in
  Type MC cable or in raceway. For ambient temperatures
  exceeding 30°C (86°F), conductor ampacities shall be corrected in accordance with Table 690.31(A).