Here’s a rough idea of how something like that might work:
- The overworld is a board with hexagonal cells.
- Every cell a small associated map with at most 6 entrances (one for every adjacent cell).
- As in Wesnoth, a cell can only have one unit stationed at it at a time.
- Every unit has a certain number of moves which are used to move around the overworld and can perform one action per turn.
- Performing an action consumes all remaining moves.
- A granger or a builder can enter the first-person view of the cell it’s stationed at and build/deconstruct. This counts as an action and consumes all remaining moves.
- Structures take a few turns to be built (the exact number of turn depends on the structure type).
- Every cell can contain at most one armory and one medistation. The number of defensive structures per cell is not limited.
- Unlike the real-time mode, structures like armory, medistation and booster can’t be used (but can be damaged) in first-person view, even when fighting.
- A cell with enemy structures in it can not be entered, but can be fought with even if there’s no unit stationed at it.
Zones of control (Wesnoth style)
- All units except dretches and basilisks control their adjacent cells.
- If a unit enters a cell controlled by an enemy unit, its remaining moves are consumed (but it can still attack).
- Dretches and basilisks can ignore zones of control.
- When a unit enters a cell, it’s positioned at the entrance it came from.
- A unit that hasn’t used its action yet can enter the first-person view of the cell and reposition itself (for example, a dretch can walk up a wall for an ambush). This counts as an action and consumes all remaining moves.
- A unit which can fight any adjacent enemy unit. This counts as an action and consumes all remaining moves.
- Both players enter the area view of the defender’s cell and are given 3 second worth of warm-up time (no looking around).
- The attacker starts at the entrance it came from, the defender stands at the
- The fight continues until one of the units is dead, 30 seconds pass, or the attacker unit retreats to the entrance it came from.
- A unit stationed at a cell with a medistation or a booster in it will be healed at the beginning of its turn.
- A unit that is stationed at a cell with an armory or any alien structure can evolve, buy ammo and swap equipment. This counts as an action and consumes all but one remaining moves (so that the unit can leave the cell and let the next unit in).
- In first-person view, defenses work like in normal Tremulous - they attack the enemy.
I have no idea what would work best.