Sponsor a Visa for Non-Eu boyfriend

[stella11]

Hey guys, I have been following this forum for a while and I have finally decided to ask for advice.
I am an Italian Citizen, who has been living in UK for almost 5 years, exercising treaty rights. I am planning on applying for a resident permit as soon as the time comes, and in the meantime I have been thinking to what it would be the best way to allow my Japanese boyfriend to stay in UK.
He is planning on getting a youth mobility visa, valid for 2 years and once that expires we're going to have to find another way for him to stay in UK.
The easiest way seems to be that of getting married and sponsor his spouse Visa, although I am not exactly pro-marriage, so I would prefer to avoid that route.
The second option seems to be applying as unmarried partner, but that seems to require 2 years of cohabitation, which won't be a problem, but would require him to go back to Japan and wait for a decision from there.
Is there any other option that I haven't taken into consideration and that could be of any help?
Thank you

[Casa]

Have you been living together in a durable relationship 'akin to marriage' for a minimum of 2 years and have to documented evidence to support this?

In order to qualify as an Extended Family Member (EFM) the ECO will want to see joint commitments over the qualifying period such as shared finances, joint tenancy and both names on utility bills etc.

[stella11]

Not yet, as we live in separate countries.
But whenever he comes over we will be living together.
The problem is that even if we live together for 2 years, he's gonna have to leave after that because his visa will expire.
Is there anything that can be done to prevent that?

[noajthan]

Apply as EFM after 2 years on T5 if UK is still in EU.
Or swallow principles and marry.

[stella11]

Riiight
Thanks!