I posted something similar in February - I just want a basic bank account first, with the added features coming later. I’d happily pay £5 a month for the account if features were added. I suspect they feel they need to justify the fees by adding features which is why they’re doing it the other way around - building a fully featured account then letting people join, it avoids the backlash over the Monzo Plus offering.
I use FreeAgent for all my logging. I will probably use Pots to keep tax money aside, and monzo.me could potentially be handy (though Im usually invoicing large companies rather than other freelancers) but the thing I most want is having all my banking in my monzo app, and notifications when invoices have been paid/money has been spent.