So if they where to admit Ukraine into Nato but explicitly exclude the current conflict with Russia, barring nuclear/wmd escalation what issue would there be?

In fact they don’t have to go that far, a workaround was discussed where the definition of Ukraine that was protected by NATO would be an area smaller than the national borders (to exclude the areas where current fighting is occurring, but protect currently peaceful areas like Kyiv). E.g. https://www.theguardian.com/world/2023/nov/11/ex-nato-chief-proposes-ukraine-joins-without-russian-occupied-territories