Feature request: push loan parts / sell to nominated user

I suggest just continuing as you are.

Each of us will in the future presumably have legitimate reason to have at least three different accounts: unwrapped, ISA and one per pension pot. One per pension pot can arise in part because it is illegal to combine pots that are in drawdown.* A "beneficial owner" identifier is one possible approach to addressing the issue, with certain limits being per beneficial owner rather than per account.

*You can add more money to a pot in drawdown by crystallising some uncrystallised portion of a pot into it, it's just combining two drawdown pots that isn't allowed. Crystallising is the formal term for a range of actions that happen when benefits are taken from a pot in some way. Pre-crystallisation means that a tax free lump sum can be taken, after means that it's already been done or it's too late is the most obvious distinction between the two states, the ban on directly paying new money into a crystallised pot is another.

Is it OK for husband and wife to have an account each, even if they generally pool their assets?

I've just skimmed through SS T&Cs, and there is nothing in there that says you can't. You won’t get a referral reward though;

The T&Cs are loosely worded as to whether there is no bonus for introducing YOUR partner or spouse, or 'the partner or spouse of an existing member'. 8>. I suspect SS would like to enforce the latter interpretation!