IGNIS and ARDR coins will be allocated to user accounts in the Ardor genesis block. Their distribution will be based on a one-time snapshot conducted over the Nxt blockchain (the "Ardor Genesis Snapshot")
So basically, there is only one snapshot. You can't do your strategy.

wow guys nice up price ) hehe
tell me why nxt so good go up when all alts go down )
also about naut - its was fork nxt or only lable somthing like we based on nxt platform thankz

Has any reputable exchange officially confirmed that accounts with NXT balance at the time of the snapshot will receive the appropriate number of tokens (for exchange/withdraw at a later date)?

Not so far. Edit: Only AEX so far.
Bittrex has confirmed to support Ardor.

25 or 28 December. Just 2 weeks left.

A nxt, an ardor, these two projects are really too low-key, if not the arrival of ignis, their price is very willing to lying on the $ 0.1 price

The desktop wallet automatically connects you to a remote full node while you are downloading the blockchain so that you can do everything despite you not having the fully synced chain. I'm not sure if it is advisable to enter your passphrase as long as you are connected to a remote node though. 

To be on the safe side, I want to recommend anyone to download the desktop wallet and move your coins over there. Its better to control the keys on your own when participating in something like this, its all about money here.
I would not risk not being credited my coins, just because I was too lazy to move my funds. Exchanges nowadays are shady, I would not trust them even if they promise something.
Better safe, than sorry.

I do hope there will be more waves of pump for both Nxt and Ardr.
BTW, I think current ratio of Ardr/Nxt, which is around 1.5, is more reasonable.