Ok, so if this were an SMP mod, what exactly would the code do every tick?
Would it iterate over every single block in the wall or sphere to check if the block is missing, every tick, all the time? That is the reason the IC1 shield failed miserably. The algorithm is so inefficient it killed the fastest CPUs.
Or did you use a different method? Can the blocks that compose a force field be destroyed with a pick? Explosives? If the block is destroyed, how does your algorithm repair the missing blocks?
Second, so for applying damage you look for entities within a sphere near the shield generator and the ones that are close to the actual shield blocks are the ones that take the damage? How often do you do this check?
Reason I ask is that shields, especially ones that also do damage, are a crucial feature this mod needs for SMP. But it has to be implemented in an efficient manner or you will not be able to have more than 3 players on a server.
Alblaka explicitly stated in this post here that he is NOT working on a shield generator for IC2 because the algorithm he used is too inefficient. If you have an idea for a better algorithm, you should implement it. I detailed the pseudocode for one that IS efficient and would work even for many shields on a single server if you are interested. Or, if you open source your mod, I may take a crack at it this weekend.