So in this perfect world where we're implementing your system, steem price is constantly going up

You are misunderstanding, the price will also go down and some users might lose some influence, but it won't matter because they bought it already and that increased the price. Some new users will want more influence which will increase the price again, then the price might go down,etc..but the idea is that more people will buy steem power to get influence than people will sell the steem power that they already bought.

Steem price will have to increase to handle new users, so yeah that should definetely be the goal. I often hear people say that an increase in number of users will lead to an increase in price, this is completely false in the current form, users have no incentives to buy steem power right now and curation rewards is only an incentives for a minority of users, most people who uses steemit have no idea about them.