Such as what? A solid lump of metal can't have a variable frequency, such as we saw from those torps.
Installing a frequency modulator projector, or a poloron decoupler, or a frequency mimicer????
Don't start. For one, if they can stop lasers of a given power then they can stop anything else of that power, and secondly the ship is far from immune to laser fire - there were several instances of the E-D being threatened by laser-armed craft.
Not pertenint to the topic at hand. However, as it was never explained why modern starfleet nav shields are so effective against lasers we can't know for certain if its a matter of sheer power, or some side effect of the tech employed. And the whole statement about lasers came WHILE the E-D was being threatened by said ships with lasers.
We've also seen no sign of torpedoes being fired on, although that seems to be more of a problem with hitting a small, fast, manoeuvring target than anything else
Aside from the exception Reliant just noted, I can't think of any examples myself. As as you've just noted, they are small and rapidly manuvering. It doesn't seem logical to put combat shields on a fire and forget torp.