Are the second edition rules combinable with the Battles of the Third Age additions (not using Collectors Edition)? Because it seems the changes of the 2nd edition were created without this expansion in mind?
If you are referring to the Battle games (Rohan & Gondor Scenarios) they are still compatible as you need the figures from the base game and they are the same in both editions of the main game.
What you will need is tokens to use as Damage Counters in the Scenarios as no such counters are part of the Second Edition (in the First Edition they were Replacement Tokens).
If you don't own the Collector's Edition I don't believe you will ever be able to use the Twilight of the Third Age (the expansion part that expands the base game) with the Second Edition as the card sizes make that impossible (unless you create the Event Cards yourself).
There is allready an expansion for the Second Edition being playtested and Roberto DiMeglio (one of the designers) has said that it most likely will NOT be a simple rehash of the previous expansion. That is all I can say, as I am not at liberty to disclose anything from what we are currently testing.