I agree that this has to change.
The simplest solution must be to allow boarding in port - with little delay or attrition if it's a proper harbour - then normal attrition of the troops when boarded, increasing to really horrible attrition after a month or so (cramped insanitary conditions). Add in pop-up messages to say "boarding in Caux is complete, where to Sire?" or "Raleigh's Expedition getting depressed in port of Anglia" and the problem is gone.
The only time the troops should have to go out into a sea zone to board should be if they are boarding from a province or TP with no harbour.
The simplest solution must be to allow boarding in port - with little delay or attrition if it's a proper harbour - then normal attrition of the troops when boarded, increasing to really horrible attrition after a month or so (cramped insanitary conditions). Add in pop-up messages to say "boarding in Caux is complete, where to Sire?" or "Raleigh's Expedition getting depressed in port of Anglia" and the problem is gone.
The only time the troops should have to go out into a sea zone to board should be if they are boarding from a province or TP with no harbour.