Deluxe Edition / Improvements
First, the record sheets need some work. Realistically, a 3x5 card per Hex is needed, as each Hex can have multiple improvements that affect its defensibility and production. The example sheets have 1 line of space per Hex, which is not enough to really note the effects of multiple Assets/ Improvements/ Fortifications. The expanded record should also include a reminder of how to apply multiple modifiers to production. Also, spaces for recording "Bad Event this season, temporary 50% loss of production" or "Good Event this season, production +50% this season" would be helpful. Guilds present and their levels should be recorded, as well as any ongoing adjustments to Upkeep should be represented.
Some other terrain types might be good to add, like rules for placing Oases in desert areas. I liked the inclusion of "Underground" as a terrain type, as most other products have ignored it, but perhaps to re-balance a larger list more would be needed (ie., Fungal Caverns, Pool Caverns, etc.). Also, for that deeper fantasy feel, what about "Cloud" as a terrain type ?

Kelp Forest ? Coral Reef ?
Considerations for non-standard Calendars would be good to add as well (I personally use a calendar of 3 10-day weeks per month, 12 months per year).
More realm spells would be nice. Possible Errata: The Impenetrable Woods realm spell is listed for both Druids and Arcane Guilds as a level 2 spell, but the spell description only includes Arcane.
Some improvements and events mention that they may only be effective in hexes adjacent to the ocean. However, some of them should also be effective if there is a large Lake nearby. This is not true for all. The event about traders is properly restricted to the oceans, for example, as written; however, the Fishing Fleet improvement would be suitable for use with a large lake (2+ contiguous hexes ?).