It's been said before but I'll say it again, ambassador is kind of meh when there's no engine, but elite when there is one. This is clearly a case of no engine, so the double amb opening is pretty bad. That said, there are a few decent BM options. Trader works quite well as a BM amb counter, though it's likely countered fairly well by militia. Ditto your stash plan. It should beat ambassador without a huge issue but lose to militia. So I think militia/BM is the best opening, though after you see your opponent open ambassador, you have lots of options.
