I started a game as Pomeranian tribal in the early middle ages bookmark (Charlemagne). Things went really smoothly as a tribal, large armies and I easily defeated the neighbours. The biggest challenge is the succession system, but that can be dealt with by fighting a few wars every time after succession (a hassle but it doesn't destroy your state).
My goal from the start was to eventually transition to a republic and build a trading state that encompasses the Baltic and Scandinavia. This is proving harder than I anticipated. As soon as I transitioned to a republic, my number of troops decreased by a factor of 5-10! I had almost 5k troops I could raise + those of vassals as a tribal, now I have around 500-800.
This wouldn't be such a big problem in itself, as I can hire mercenaries, but since AI looks purely at the levy when deciding which neighbour is weak enough to be attacked, I am getting attacked by virtually everyone around me. I've become a target even for vassals of my neighbours. This makes it difficult to have enough breathing room to raise cash needed for the next invasion, let alone to develop my state and build up the levies. Not to mention prepared invasions where I seem to be everyone's target of choice.
Did I just transition too soon? One of my neighbours (Saxony) had already transitioned earlier to feudal and didn't seem to experience such a large drop in levies, so seems like it's possible to do it without being destroyed.
I worry that if AI wins the next election (which is likely since my treasury is always low due to having to hire lots of mercenaries) then my fledgling state is doomed.
How do I survive this?