a complete swallowing of Ukraine
...which would trigger (of course, before Ukraine collapse - strategic depth and all that) Polish-Russian war and introduce many, perhaps too many, unknowns to all the plans and equations.
As far as the RAND report is concerned, I think Cold War 2.0 would probably be the most favorable outcome for Poland...
... as it would achieve our long term goal of restricting Russia's activities mainly to Asia, where they would have to eventually turn into a Chinese semi-client (this 'semi-' bit is important) state and effectively stop being a threat to our independence, and putting Poland in place of Germany as the most important player in the NATO defensive strategy in Europe.
Long lasting stability would require one more factor that RAND report seems to be missing - taking Belarus out of Russian influence zone and making it a part of the safety buffer together with Ukraine. It would be expensive but money for such vital projects will have to be found. So, effectively we would have two safety buffers: Belarus-Ukraine closer to Russia, and Intermarium (with nuclear Poland) as the ultimate shield of Europe. Everything would seem to point in this direction.
The most important thing is that in any scenario we avoid the "Reverse Kissinger" disaster (i.e. USA and Russia alliance against China).
a game changer
There have been many game changers up to date that actually already happened. Among the most important ones is the joining of NATO by Finland and Sweden - extending the front and practically rendering Russian Baltic Fleet useless. It also allows Poland to concentrate on building up our land army, as naval duties in the Baltic will fall on our allies whilst we can limit ourselves to on-shore rocket batteries. Unfortunately, we are already getting three
Miecznik project frigates - it's too advanced to give up now - so we will have some redundant naval force. Oh, well... the frigates will look nice on national holidays celebrations or something
*rolls eyes*Another game changer is the fact that Ukraine showed that a superpower (2nd rate but still) can be stopped in a direct, conventional war by a middle-sized country. Of course, we can argue that we already knew this ever since Vietnam or Afghanistan, but this is a bit different. We have a middle-sized country stopping an alleged superpower in a direct, conventional, all-out land war. If this is possible, then achieving the same by a coalition of middle-sized/small countries is also possible (i.e. Intermarium).
In any case, Ukraine needs to be reinforced and the numbers you gave (which suggested the possible collapse of the Ukrainian Front) - if they are accurate - should prompt NATO (and definitely Intermarium which is threatened the most) to think of additional ways of further strengthening AFU.
Of course, we have to remember about the issue of Królewiec (there's money to be spend on it too), and eventually even reinforcing Russia so that they don't collapse too soon, and the US is already thinking about it (but that's a longer perspective and you won't read about the details of it in open reports on the internet), so don't worry, Bobi, the USA themselves will help you so that you don't fall into pieces. :) We don't want China too strong either.
Anyways, my little scenario from the previous part of this thread (yes, I have too much time on my hands recently :)) asssumed 0% NATO response and 0% USA response in case of the Polish-Russian war, and still it gave us an acceptable chance of success. It was, of course, only mental gymnastics (as Crow would say). ;)