I think the easiest way of expressing complex numbers is directly translating a decimal positional system that everyone already knows.
We can express numbers 0 to 9 already: wan, tu, tu-wan, tu-tu, luka, luka-wan, luka-tu, luka-tu-wan, luka-tu-tu.
Just spell the numbers in their respective positions using pi.
This year is 2017 - suko suno ni li nanpa pi tu pi ala pi wan pi luka-tu
Not the most practical but again, according to pu is better to just not use those kind of numbers. If we need to, we should stick to the simplest solution within toki pona framework.