I'm not a Doctor, but here's a few observations.
If I make a cheddar, I put in X amount of salt. When it's young, and when it's aged, the salt content is the same (ignoring small percentage changes for moisture loss over time.)
The same is true for almost all cheeses except those stored in brine.
That said, an old and a young cheddar side by side on a supermarket shelf don't necessarily have the same salt content, they may have had different amounts added at manufacture.
Sharpness in cheese comes from age, and low sodium cheeses are unlikely to be very old. Buy some, stick them in a fridge for a year, and they will probably be MUCH tastier.
You could make low sodium cheeses, then you will know the exact contents, but you may not be in a position to undertake this and wait the required time for ageing.
My suggestion would be a 2 part one. Buy a batch of low sodium cheeses and put them away to age, trying one every 3 months. In the interim, satisfy your craving as you suggested by mixing Low Sodium cheese with a small amount of the most powerfully flavoured cheeses which suit the application. Parmesan and Blue would be my first pick in Australia, but in Europe you would have many more to pick from.