I certainly agree that the Escort is useless in the default configuration, but it's a perfectly good picture in every race definition! Don't waste it.
Just bump the sizes up a bit and they are more useful. But don't over-do it. I think that the mod idea posted by Tim McElwain on the SE4 list on yahooGroups is a bit excessive. There needs to be a major size difference between ships and bases in order for bases to be worthwhile and there is a certain proportion of ship size to component size inherent in the game design. I'm working on a mod now that will make the Escort 200kt and then jump 50kt to Frigate at 250kt, then 100kt per level as now for the Destroyer and Light Cruiser (350kt and 450kt). This makes these classes a little bit more powerful and flexible but doesn't completely throw out the game balance in the original setup. Then as the cost of researching levels of Ship Construction gets greater the returns get greater. So, a Cruiser will be 600kt rather than 500kt (150kt increase on the level rather than 100kt) and a Battle Cruiser 150kt more, at 750kt. Battleships and Dreadnoughts would be 1000kt and 1250kt, giving a 250kt increase, and then the base ship will remain at 1500kt. This is a much smoother "curve" to reach the base ship than the default arrangement, too.
Space Stations are already 600kt in my personal mod, and a battlestation is smaller, at 1200kt. But this is to make room for TWO sizes that use the Starbase picture: The "Star Fortress" at 2000kt and the Starbase at 3000kt. With the starbase being fully twice as large as the base ship, you still have a decent incentive to use them since they can easily stand up to any single ship and quite a large number of smaller ships.
There are some other game-balance factors that I am working on, like engines per move and number of life support/crew quarters at various sizes. I hope to start a game with my new setup in a week or so, though.