one for /r/LegalAdviceUK

Don't forget to figure out the implications upon division of assets in divorce/breakup

Option 2 would be the best to easily reverse

I did something different. I registered a partnership at hmrc (a regular partnership not an LLP) the partnership hold benefit of the property, no owner documentation is updated (deeds, mortgage unchanged)

This now classes the BTL as a property business run by the partners. The partners can agree on the amount of profit they take based on the rules they have set up. I have decided my wife will take all of the income as she does (ahem) all of the work.

You would not need to be added as a licence holder for the HMO per se. If land reg details changed to reflect you as a joint owner or as having any other other equivalent stake in the property then you would need to get a variation of the licence done to reflect this

There is usually a condition of the licence that regarding this requirement.

You may be interested in Form 17, but i think your partner has to be a co-owner. They dotn have to be on the licence. https://www.taxinsider.co.uk/jointly-held-property-splitting-income-using-form-17

Is it possible to create some sort of rent to rent agreement?

You rent it to your spouse for 50% of market rent

Your spouse rents it out at full market rent

Essentially each person shares 50% of the total rental income