OK, so I've implemented an escort stat:

to turn it on, modify config.h.

There are a few options:

ESCORT_STAT 
turns on tabulation and tracking of the escort stat.  It
is not backward-compatible with old playerdbs.  This is
on by default.

ESCORT_STAT_FOR_RANK
includes the escort stat into the rank calculation.
This is disabled by default.

ESCORT_DEBUG
messages everyone when escort credit is granted.
This is disabled by default.

Here's some info on the escort stat as presently implemented:

2) Escorting stat implemented.  
Look at it by sending yourself
a message "stats".  Escorting is considered equally
with offense, planets, and bombing for rank.

These things get you escorting credit:

  a)  Killing someone who is threatening your carrier(s)
      i)  the more armies the carrier(s) have, the more credit
          up to 6 armies.
  b)  dying in defence of carrier(s)
      i)  the more armies the carrier(s) has, the more credit (up to 6)
      ii) you have to die between the carrier and the threat,
          or very closeby.  You do NOT get credit if you blow
          up on the carrier.
  c)  assisting a planet take
      i)  any friendly players present at a take get escort
          credit, even if they died before the take, unless
          the takes longer than 9 seconds from the death.
      ii) Unopposed takes give no escort credit.
      iii) credit granted is proportional to opposition and
          inversely proportional with the strength of the escort.
          i.e., credit goes as number_opposing/number_escort
  d)  you do NOT get credit for escorting your self.  However, you
      WILL get credit for escorting other carriers than yourself 
      even if you carry.

This is the new ranking table:

Hours:   Sum of ratings:     Rank
0        0                   Ensign
2        1.3                 Lieutenant
4        2.6                 Lt. Cmdr.
8        4.0                 Commander                 
15       5.3                 Captain
20       6.6                 Flt. Capt.
25       8.0                 Commodore
30       9.3                 Rear Adm.
40      10.6                 Admiral