Would I be accepted at Japan uni BA of econ?

I would like to study a bachelor of economics in Japan as soon as possible.

I am 24 years of age.
I have Australian and Irish citizenship and have spoken English as my first language for 99% of my life.
I have previously attended the University of Western Australia for a dual major of bachelor of science, majoring in computer science, and a bachelor of arts, majoring in architecture, in 2014 (I was accepted in 2013 but deferred for 1 year). I dropped out after around 7 months, during my second semester due to a conflict of interest, personal issues, dissatisfaction with the academic standards of the department of arts, and lack of motivation due to choosing a career and education path based on prestige.
I have little to no Japanese language ability apart from being able to understand the meanings of about 2200 kanji, (not the readings) and about 2000 vocab words, with terrible grammar. I would be able to pass the JLPT level 4, and anything above would take a lot more study.

I understand that each institution has its own admission procedures. I am not confident in my ability in the EJU. However, I am aware that I would be classed as an international student, putting me outside normal admission standards. I would also be seen as a mature student, putting me further outside normal admission standards. I have also been admitted and attended a university which continually scores within the top 100 universities worldwide in various testing outlets, putting me further outside the normal admission standards again.

As for the break over the past 3 years, I have been pretty much-doing nothing. Not working, not studying, nothing. I have spent that time like any early 20's bum would, playing games, bumming around etc. But I also spent that time setting things right in my life. Sorting out the aforementioned personal issues, and getting my head straight so that I know what I actually want to do in life.

I have lived in Japan before for 2 and a half months. I am also not the type who wants to go to Japan to escape from life, or to hope that they can leave their problems behind.

Would I ever qualify for an undergraduate economics course in Japan?

I guess this question is hard to answer.
WHY you do not try to contact the university?

If you want to enter you better to start try doing your things by yourself

EJU is only for people who want to enter programs taught in Japanese. I think there is no way you can pass this exam with your current level.

No such thing as a mature student category in Japan - you would be treated the same way as every other applicant.

Assuming your high school and university grades are OK, there's no reason you wouldn't be accepted to an English-medium program.