Is investing 70% of my capital in variety of ishares ETF's in US S&P or Russell suites, DJ EU Eurostoxx and UK FTSE indexes really a good equity diversification
If you invest this way you are investing in just 2 asset classes, i.e.: foreign developed equities (US S&P / Russell and UK FTSE) and domestic (i.e. EU denominated) developed equities (DJ EU Eurostoxx).
Also intend investing 10% in emerging markets, 10% in cash, 10% direct Irish equities)
Emerging markets is an asset class but Irish equities are just a tilt in domestic developed equities. Personally, I wouldn’t (and I don’t) put 10% of my investment in IE equities, they make up just 1% of world market cap).
Cash is not an asset class, it’s just something you hold as a precaution against personal risk (i.e. losing you job or short term money needs, e.g. for a car, deposit for a house), etc. If you hold large cash balances you need a way to protect them against inflation.
You should also consider investing in, for example, commodities, global property and foreign government debt as asset classes. You can do all this via ETFs. You could look at a few examples of asset allocation, or get ideas for potential asset classes, from sources such as the NTMA’s National Pension Reserve Fund
http://www.ntma.ie or Jim Swenson’s Yale Pension Fund
http://seekingalpha.com/article/41738-how-to-invest-like-yale-s-david-swensen
for ideas. (Or read Rodger Gibson’s book Asset Allocation: Balancing Financial Risk).
If I go ahead with my proposed 70% allocation if possible should I seek to keep the $ in a doller account and £ in £ account - until the exchange rate improves.
ETFs have base currencies, but you have to buy and sell them in euro, assuming you buy through an Irish broker.