My current position is approx. 33% BTC/ETH/EOS. What would be your recommendation for a balanced crypto portfolio for the next 6-12 months?
Bitcoin's ratio for overall stability of the portfolio will likely be somewhere around 50%. That being said, I wouldn't really go for both ETH and EOS with how things can turn pretty nasty for one of the two in the coming months. It's important for people to understand that in most similar cases, capital shifts occur rather than actual fresh capital flowing into coins.
If EOS ends up gaining momentum, and the majority of the upcoming ICO's will run on top of that platform instead of Ethereum, which is possible, then Ethereum will bleed for sure. What happens with your portfolio in this situation is that your EOS gains will be nullified by Ethereum's decline. Also don't forget that EOS holds +$4 billion (with the lower price probably closer to $3.5 billion) worth of Ether, which is pretty insane.
It's all up to people to decide what they will buy into and hold, but it's at least something to take into consideration.
You have to think if EOS play their cards right they could kill of ETH if they really wanted to. If they can deliver they'll naturally start gaining ETH users as you said, on top of that if they time it right in terms of selling the 4bn or so worth of ETH that could greatly hurt the ETH price to the point of no recovery almost.