From: Greenville, SC
I am reading Churchill's series on WWII and specifically in the section about the preparation for Sealion and it has given me a few invasion related ideas I thought I would throw out. Just for the record, the issues with invasions in Warplan have been GREATLY IMPROVED from release, but I personally believe it is too easy to invade early in the game and also too easy to move from port to port avoiding naval interdiction. Others may disagree.
1. Much like air units can be put into a mode where they intercept, it would be great if there was a mode (maybe a third toggle for the garrison mode button) which allows a land unit to be put on "intercept" against an invasion. If they can get adjacent to the invasion hex using 50% of their operation point, they would move adjacent to the invasion hex. The British knew they could not defend all the landing points, but they did believe they could have 20k+ troops at any point within 24 hours. Right now in Warplan the land unit reaction to invasion is often too late.
2. Tie the number of landing ships allowed to be built to a naval tech. This would limit early invasion sizes and require tech investment to invade on a large scale later in the game.
3. Provide visibility into the opponents total number of landing ships built and being built. The British had good intelligence of landing ships at ports.
4. If a naval unit is within 2 hexes of a embarking port, perform an interception - this provides some ability to "blockade". Perhaps there is even a third toggle on the naval unit between fleet->patrol->blockade and only units that have "blockade" would attempt to intercept at the port of embarkation and only if within 1-2 hexes. But I have seen too many situations where land units are in a port with enemy naval units all around and they simply sail off to another port with no actions by the enemy naval units.
Just some thoughts. I feel like Warplan is SO CLOSE, but this ability to so easily move on water and also invade is its big remaining challenge. With Pacific coming up, these might also provide a big boost to the naval aspects.