My analysis of the U.S. Constitution counts about 80 words or phrases that are somewhat ambiguous, and give rise to most of the interpretation/construction controversies. I have highlighted those at http://constitution.org/cons/constitu+.htm , Most of the rest of the Constitution is fairly unambiguous. One might quibble about this analysis and my count, but let's accept it for the moment. Textualism works well enough for that part of it, whether one considers the document written in lay English of 1787, or in legal English.
Most of those eighty are written in legal English, which requires reference to 1000 years of English legal history, and may extend back 2000 years to Roman or Greek law or another 1000 years to Hebrew law.
It is not necessary, initially, to develop a single comprehensive theory of legal construction (originalism) for all eighty. Take one at a time, and develop a theory for that one. Then move on to the next one. If two or more theories have commonalities, unite them into one for those phrases.
Perhaps we eventually arrive at one theory for 70 of the phrases, another for two or three more, then a few more for the rest. That narrows the scope of the theoretical search, making it more comprehensible and more manageable. Who knows, we might actually wind with one that unites them all.
This is the approach I have tried to take. The combined theory is not simple, but it works. It can be applied quickly and definitely.
To solve a theoretical problem, first divide it into manageable parts.