The erection sequence is a commercial decision, not an engineering one

On a greenfield site the crane goes where it suits the crane. On a site with something already running on it, the crane goes where it does not shut that thing down, and those are rarely the same place. Sequencing around a live yard costs money: more crane moves, more travel, sometimes a second visit. It is almost always less than the revenue of the operation it keeps open, and it can only be designed in at tender stage. So tell your fabricator what has to keep running before they price it. Afterwards it is a variation.