I am kinda hoping that at some point added value to SIM holding, does make it possible to move in both directions with a sim peg of 0.005, but we are a long stretch away from that point.
concerning the luxury tax, it's a tricky one. For now i think it works fine and it does not really compare to being in debt as in Rabona. There's just not enough sim to pay for full social support, so income is zero and support per citizen is lower than the standard 0.02 SIM. I can imagine a sort of opposite popularity effect, where population shrinks when social support is lower than 0.02 SIM.
Or maybe a ranking where all stats are added to a final number: so population + sim sim income + popularity + education + creativity + amount of cards. I am sure the last word hasn't been spoken on this, but for now i think it works pretty good. In my opinion building a zero income city is a valid strategy, which brings interesting battles and keeps certain cards valuable, which may otherwise become almost in. Which makes it less interesting for the "professional" card sellers to keep doing what they are doing.
RE: Dcity: State of The Union.