From an end user perspective I saw two way to have this implemented: automatic or manual. From the back end, it is just like ChrisDem said, a consecutive application of D/T filters all OR-ed together. In the automatic mode, Cachly would be able to look at my online profile (as quoted earlier) and grab the data from the current D/T matrix. No need to keep all finds within Cachly. The user would have to provide the "loop number", which is the minimum amount of caches for each D/T combination. The matrix is then processed and each combination that has less finds than the "loop number" becomes an OR condition in the SELECT statement.
In the "manual" mode the user would provide a list of D/T combinations that should be filtered on. A specification in the form of 9x9 checkboxes would be sufficient for that. That's if this is implemented as a single "filter".
In iCaching it is possible to add multiple D/T combinations in a filter:
In this screenshot all caches that are either 3.5/4.5 or 5/3 .. 5/5 are selected. While this is full flexibility, it becomes more difficult to see what is included. The 9x9 checkboxes make things much clearer.
Again, I don't think the back-end is very difficult, the largest amount of time might be in the usability. That is not an argument in favour of this request but I hope this clears things up a bit.