Check the post in the sister thread: PNK minting and 2nd token sale - rights issue - preferential treatment for current holders - #6 by marsrobertson
I was also thinking about opening for existing holders some time before the main sale opens.
Now realizing it could be an obstruction to marketing efforts - two dates 
On the other hand:
- it’s simple enough to explain in one sentence: “existing holders have extra 24 hours”
- it’s a good incentive to accumulate more PNK before the sale
Not sure about this example. Having 0.5 ETH of PNK and being allowed to buy 1 ETH at special prices?
I’m also worried about the complexity of calculations (even on the front-end, having time, not worrying about gas)
Alice buys 1 ETH and the buy() function fills 0.5 ETH at 0.00005 and 0.5 ETH at 0.000051 - now we need to know the exact state of the sale - will all the purchases and all the orders to properly calculate…
Opening sale 24 hours for existing holders seems simple. A few other guys suggested it. I support this idea. I was thinking about technical implementation. Check the PSEUDOCODE: PNK minting and 2nd token sale - rights issue - preferential treatment for current holders - #6 by marsrobertson
If you like it, I’ll write the acual code and issue pull request.