The phrase "grand plan" means having a big, detailed and thoughtful strategy or idea to achieve a specific goal or complete a complex task. Full definition
We'd make grand plans of having a meal out at least once a month; we'd still take regular trips to the cinema and see the occasional show at the theatre. (relationships-scotland.org.uk)
I often set out on a project with grand plans and lovely pictures in my head only to be disappointed by the result. (mammacandoit.com)
Ah, the new year: a time for us all to make grand plans. (business.time.com)