Sorry I got to this late. You raise a good point, and have basically nailed the crux of the issue. Just for background, I've worked as a tax policy analyst for about half my career, advising Australia's federal executive government. After quite a bit of thought (going on a few years now), my conclusions are roughly the same as yours. Our options are either:

1) Give up on corporate tax and shift the tax burden on to less mobile bases (e.g. land, consumption). This scenario seems to be slowly playing out across the developed world (perhaps a bit faster in Ireland's case...)

2) Engineer some kind of grand international agreement on corporate tax rates, kinda the Bretton Woods system for tax. This would be necessary because there's such a strong incentive for countries to 'undercut' each others' corporate tax rates (to attract foreign capital investment, tax havens being the extreme example of this). Such an agreement would require: a specific (but not too specific) agreement on minimum corporate tax rates, the participation of countries representing most of the world's production output, and provisions that levy punitive tariffs on non-complying, and non-participating, countries that go below the minimum rate.

Even up until recently, I've thought (2) to be basically impossible. But in the past few days I've begun to think maybe I was wrong to rule this out completely. In a strange way, Trump's presidency might be the golden (and possibly only) opportunity for this. He seems to be just the right amount of crazy to do it. I couldn't imagine an 'establishment' president going near something like this. And I think only the US could lead such a process, maybe with some quietly pre-agreed support from China. Given the capital flight China is currently plagued with, their precarious public finances and their main central banker publicly stating support for some kind of international agreement on capital controls (I believe he actually invoked Bretton Woods), it seems like a few stars are aligning.

I don't want to give you false hope here. I still think (2) is very difficult and unlikely. It would have to be 'sold' to government skillfully. Perhaps our 'automated future' is the narrative to go with. Something like: As labour is replaced by algos/robots, then by definition production becomes more capital intensive. So more and more of the gains from production and trade accrue to a fairly small group of capital owners.

It's conceivable that, in the not too distant future, some of these mega-corporations will have revenues/net incomes that rival that of even large, first-world governments. At this point, they will be an existential threat to liberal democracy as they will have the means to field a sizeable 'private security force'. Not to mention the immense soft-power they will wield when they control most of the world's means of production.

So, although this may all sound crazy, it would be unwise and dangerous to allow things to reach a stage where liberal democracy is in peril. Therefore, we must tax corporations/capital in a way that leaves them nowhere to run (i.e. via an enforced international agreement on rates). Also, a fair chunk of this revenue will be redistributed to workers (perhaps it may even be enough to fund basic income), so it's good populist policy that a populist leader like Trump is well suited to selling (although he'll face significant opposition from those suckling on the corporate teat i.e. mostly everyone, including the 'mainstream' media).

Note: I'm not really keen on emotive arguments like the above, but I think some version of the above is what it would take to sell a radical proposal like an international agreement on corporate tax rates.