1) This breaks the API, which makes it unlikely to be accepted as-is.
No it doesn't. Existing queries will keep on working (as explained in the first post).
It is not 100% backwards compatible.
2) It is such a small amount of information, I do not see the difficulty in querying up to max-count.
As it is today if i have thousands of transactions and want to view the oldest one I have to get (and store) all the transactions. Think what might happen if my wallet wasn't stored locally... it would mean getting MBs (potentially over slow connections) every single time!
Even with thousands of transactions, that is not many bytes, certainly not "MBs."