> The Shining Knight would be an obvious member, since he is British and, according to All-Star Squadron, was based in Britain as CWinston Churchill's bodyguard. The Spear of Destiny and Grailstone would knock out most of the obvious big guns due to magic vulnerability (GL, WW, Superman, Fate, Spectre), so Commander Steel would be needed for power, Johnny Quick for speed, Firebrand (Danette Reilly) as the Torch analogue, Tsunami as the Namor analogue, Dan the Dyna-Mite as the Bucky analogue and Human Bomb as the wild card.
The Shining Knight and the Human Bomb are both affiliated, however.
Trying to gather closest Invaders-equivalents I could, I would substitute for Sub-Mariner: Aquaman if pre-Crisis, otherwise Neptune Perkins
Dan the Dyna-Mite is more of a Toro substitute. For a Bucky substitute, the only unaffiliated kid hero I can think of is Genius Jones.
Roy Thomas had an unofficial with the "Invaders" (similar to the unofficial Avengers/JLA crossover where you had the Avengers vs. Squadron Supreme and JLA vs Heroes of Angor), where you had the Invaders go against the Crusaders (a thinly veiled Freedom Fighters) while the Freedom Fighters went against a thinly-veiled Invaders called the Crusaders.
The Crusaders of the DCU were made up of Americommando and Rusty, Fireball and Sparky, and the Barracuda. The Freedom Fighters fought this group fo Crusaders in issues 8 & 9 of their series (in 1977).
- little kon-el