The first and most obvious point on which the EU will object, is that it gives access to 'The Customs Union' without paying for membership of the club, i.e. backdoor membership which Barnier has already warned against.
So expect a membership fee to be part of the final agreement.
I suspect also that the EU will insist on closer agreement towards the free movement of people, but maybe not the whole caboodle. Although, it will look very much like what it is now, if the UK applied the rules that they have always been allowed to apply, but never did. Preferring instead to blame the EU.
There may also be some requirement on accepting some of the EU rules, not entailed in tariffs or regulations, e.g. quotas, VAT (perhaps to avoid smuggling over an invisible border)