EML

I am having trouble defining the Space Oblique Mercator map projection
in the spatialRaster subtree of EML. The problem is unique to the SOM
(any oblique map projection, for that matter) projection - the SOM does
not use a prime meridian in the usual sense (i.e., it is fixed to the
flight path of the Landsat satellite, not a geographic coordinate system).
Since EML requires the primeMeridian-longitude and unit-name attributes
to be strictly defined, the document will not validate. Is there a
recommendation from the EML community for how to deal with this issue,
perhaps making the aforementioned attributes optional?

I have included below an example of how I would define this projection.

Notes:
1. The SOM projection does not appear to be common in the remote
sensing world other than EOSAT/Landsat/IRS formats. Unfortunately, we have
much data in this projection.
2. FGDC has a separate element for this projection in their schema.
Actually, FGDC has a separate element for each major projection definition.

<spatialReference>
<horizCoordSysDef name="SOM">
<projCoordSys>
<geogCoordSys>
<datum/>
<spheroid name="International_1909" semiAxisMajor="6378388"
denomFlatRatio="0.996633"/>
<primeMeridian longitude=""/>
<unit name="">
</geogCoordSys>
<projection>
<parameter name="Landsat_Number" value="5"/>
<parameter name="Landsat_Path" value="36"/>
<parameter name="False_Easting" value="0"/>
<parameter name="False_Northing" value="0"/>
<unit name="meter">
</projection>
</projCoordSys>
</horizCoordSysDef>
</spatialReference>