(First, sorry for the delayed response.)
Correct, 25 CIB never lacked for reinforcements, although it took a lot of effort from the Army to ensure that this was so. All of details on the reinforcement situation can be found in Strange Battleground. Essentially the Army bet on a short war, and lost. Add to this the fact that the Government promised a Division to the NATO Integrated Force with a Brigade to be in Germany, along with a need to maintain an Airborne Brigade in Canada as its part in the Canada-USA defence force.
I can't speak to the 11-man rifle section being designed with LOB in mind, but it would have certainly made keeping a minimum of 8 men per section a lot easier.
As for the Engineers, I don't have anything other than the book referenced above, which deals with the reinforcement situation in general and not by Arms specifically. I do know the Engineer squadrons were big. In 1954 they were 300 (10-290) men strong.
Wish I could help you more.