Hi Chris,
I can't see this happening any time soon. There used to be an 'LE' version of PixInsight, but support for (and provision of) that version was abandoned many years ago now.
In fact, even support for the original 32-bit version of PI has had to be dropped - to allow support to be focussed on the much larger 64-bit marketplace.
The biggest single problem for supporting any tablet-based OS (as I see it) would be the GUI. There is a huge difference between a mouse-based 'single-touch' UI and a 'finger'-based 'multi-touch' UI. Coding for both of those scenarios would be an extremely difficult task to support.
Yes - you could code for a GUI on a tablet that is in use 'today' - but who is then going to support the testing and verification of that user experience as and when new OSes and UIs are released in the future. (and all of that before you stop and consider just how 'closed' the whole of the Apple organisation is - sometimes even getting things to work on a Mac environment can be difficult enough).
What you could try though (assuming that you can find a suitable App for you iPad) is to use some form of 'remote desktop control' software - leaving PI running normally on a desktop/laptop machine whilst you perform operationson the tablet.
Personally, I have tried that, and the experience just isn't that good. With the cost of second-hand laptops plummeting all the time, I just went to my favourite online auction site and, for around $200, picked up a two-year-old laptop (that some snotty youth had obviously grown out of) - and that included an upgrade to 4Gb of memory and an UPgrade (!!) from Win10 back to Win7.
That leaves my tablet free to watch a movie, surf around YouTube or Google, or even Skype with fellow astronomers - during the long cold hours of a clear winter's night this seems a far better use of the silicon in my opinion!
