As my experience is: if it is asic minable asics will come in, especially for sha256/scrypt algos.
If you want to prevent insta ASIC mine you should lower early blockreward from 100% to, for example, only 10%. So it will not be profitable in the beginning to asic mine.
There is no possibility to block miners >200GH/S for example. If you want CPU/GPU only then you should use different algo. Besides sha256 algo will allow the coin to get a nice hashrate and a stable network after some days. But people mineing with CPU/GPU will, most likely, only receive small BTC3 amount.
Another possibility to attract more peple is quite easy: airdrop.
Let people put a BTC3 signature on for example, and if they do so for about 2 weeks you drop some of the premined coins to them. In my experience, new coins with signature campaign and airdop, are very well seen in the community. People will see that you do not want to keep the premine only for yourself (the devs) but also for the community. If you would need some help for setting up something allowing you to payout the signature campaign holders, get in touch with me. I am someone who enjoys helping others, and i am quite sure, that "only" the coin cointaining BTC might sky rocket.
Don't get me wrong, i am not criticising your coin model, i am just shareing my experience as someone who is in to cryptos for "many years" now