Lower CGT for Irish investments

The main argument I hear against high CGT rates is that it discourages investment and so the economy suffers. But I imagine that a lot of people who are investing in stocks, for example, would have a significant amount of European and American stocks, and these contribute nothing directly to the Irish economy.

So why not two different CGT rates, a lower one for investments in Irish companies, e.g. 15%, and a higher rate for companies outside of Ireland, e.g. 40%?

Does something like this already exist? Or what are the potential downfalls that I'm missing?

Related to this post: https://www.reddit.com/r/ireland/s/1Of2drxJQ7 but that's more about encouraging investing personally, and I guess parties on the left would respond by saying that we shouldn't tax work more than passive income.