Damage may be a set formula, but variations do happen, I used to do the same thing you did but the damage did change. A straight move from a to b in 3 blocks and then attacking another unit does occasionally result in a 1 unit difference. It seems to happen once every while, but I know damage is also random at times.
I found the (U) ROM without the intro hack, and the movie plays without desynch if the first 422 frames are removed. (The hacked intro uses the start button once, and the game accepts the start button on frame 52.)
Orange Dawn can be done in 4 days by letting your cruiser and sub reach 1HP and sacrificing your lander and T-copter to get the needed stars for Victory March. I suppose a Double Time on day 3 would also be a 4-day win. Which one is faster would depend on whether Lash can be manipulated to not have enough stars for Prime Tactics on day 3. The next mission is probably Flak Attack instead of Orange Dawn, since Test of Time is required to reach Liberation. With enough luck manipulation, it should be possible to leave only a lone enemy infantry at the end of day 2, for a quick 3-day victory by rout.
The RNG is at 03001fd4-03001fd7. It seems to advance 3 times each frame whenever you can press A to select a target for an attack (and at no other convenient times from what I see). You can also advance the RNG by drawing paths as in my Fire Emblem run. I don't see what needs manipulating in Andy's Time, but perhaps your strategy is better than mine for a TAS. My strategy involves blocking the enemy base on day 4 after building two recons.
BTW, I'm working on Andy's Time. Proceeding in the fastest manner possible through a 7-day level is harder than I thought it would be.
I played the heck out of the orginal Advanced Wars, but AW2 I thought the storyline was corny and the graphics seemed ugly by comparison. The new, more powerful tank didn't make the game more fun, but it did add complexity. I loved the original because it reminded me of chess: there were just a few units for each aspect of warfare, and the number of possible positions is enormous. Despite have relatively few pieces, chess and go are two of my favorite games. Their complexity may make them unsolvable, so I assumed that AW/AW2 would also be unsolvable, meaning that you could never be sure if you had played a perfect game. Despite my dislike for AW2, I think they're both great candidates for TAS because they may always be improvable, leading to innovation for years to come (much like chess and go). The only problem is that the campaigns are so long. Do you have an estimate of how long the run is going to be? It may be necessary to watch on fast forward.
Here's a short run of the beginning I put together with that improvement and a few more. I used the same intro hack ROM since I haven't found a good (U) ROM yet. http://dehacked.2y.net/microstorage.php/info/1739/Advance%20Wars%202%20-%20Black%20Hole%20Rising%20%28U%29%20%28Intro%20Hack%29%20%28Mode7%29%20%5B1060%5D.vbm I've beaten the game several times, so I'm sure I could help with this run.
Desyncs on day 2. I know I've got the (U) version of the ROM, but I don't know anything about the (Mode 7) at the end of the run name.
Of course, versus Flak, you can take advantage of his slight unluckiness which results in less damage sometimes.
Not to mention the walthroughs don't take into consideration perfect luck (I'm not sure how much luck manipulation is in this game, but I'm sure there's at least a fair amount). I'd also like to see a run of this. It'd be interesting to say the least.