With Civ7 being separated into three different eras with three different combat mechanics, my suggestions for each era are as thus:
Ancient era:
Ancient era catapults are useless for anything but city sieges
Starting with swordsman, meele warrior unit types have the exclusive promotion "charge", which grants them the option "prepare for battle" . Whereas they will mark one unit, which they can move and attack on the next turn, and get attack bonus when attacking said unit
Starting with swordsman, meele warrior unit types have the exclusive promotion "sapping", which grants them the option "sapping" . Whereas they will mark one defensive building, and spend the next two turns preparing for the attack, the action will be interrupted if they get attacked . If it doesn't get interrupted, they get a combat bonus and attack as if the city doesn't have fortications
"Charge" and "Sapping" are mutually exclusive
Exploration era:
Exploration era trebuchets are useless for anything but city sieges and fort attacks
Exploration era cannons are named "siege cannons" are weak without promotions, but can be specialised for either city sieges or anti-naval warfare
Starting with the knight, heavy cavalry unit types have the exclusive promotion "breakthrough", which grants them the option "breakthrough". Whereas the Knight will mark one unit, second and consecutive attacks on the same unit deal more damage if the unit's HP drop below 90
Starting with the knight, heavy cavalry unit types have the exclusive promotion "patrol", which grants them the option "patrol". Whereas the Knight will mark two adjacent tiles, if any enemy unit moves to that tile or to any tile adjacent to it, the knight will automatically move and impose ZoC over that unit
"Breakthrough" and "Patrol" are mutually exclusive
Modern era:
Modern era cannons are named "field cannons" are weak without promotions, but can be specialised for either city sieges or anti-naval or land unit warfare
Modern era artillery and mobile artillery are weak without promotions, but can be specialised for either anti-naval attacks, land unit attacks, artillery duels or concealment
Starting with machine guns, archery ranged unit types have the exclusive promotion "suppression", which grants them the options "suppression". Whereas the machine gun will mark one unit, it will deal less damage but it will prevent that unit from using "prepare for battle" option
Starting with machine guns, archery ranged unit types have the exclusive promotion "ambush", which grants them the options "ambush". Whereas the machine gun will be integrated with an infantry unit, movement speed is limited to one turn, but defense option is stronger after three turns if infantry does not get attacked . If infantry moves afterwards, the bonus is lost . The extra defense bonus only lasts one turn
"Suppression" and "Ambush" are mutually exclusive
So basically you would like to nerf ranged siege units against other units, and I can see why...
Civ VI suppression fire from multiple cities, barracks, and a couple of cannons, would vaporize anyone in one turn...
Suppression, ambush, and Sapper promotions on the other end seems intended to boost units effectivenes in siegieng cities, or trench warfare, or both...
You still have to squeeze one unit into the last remaining hex of the city you want to defend or take, and if you can't even store two or three cadets inside the last bastion
of resistance... so if a city produces a cannon or machinegun, and a tank, one of the two has to go outside the walls... cities will continue to fall like leaves once all other suppression fires are dealt with.. I have always been against cities with their own HP, because Ai would not build not even a basic defensive unit sometime and just prioritize walls, and then some archers,
and after walls fell, the HP of the unit would not matter and die instantly. The new city capturing mechanic is still a mistery to me but I can see your suggestions as moving
towards a stronger tactical approach to all combat mechanics in general. I like it. It's creative response.
Especially Patrol I would rank top suggestion. Naval units in EU3-4 all have patrol, over multiple territories, in constant loop.
A mod in civ VI allowed for scouts to create outposts that could then be used by some other units under your command, and the outpost would boost view of +1 tiles in all directions.
I would like it could make it in the base game this time. Maybe combined with Patrol... with an advanced button to add some waypoints for the patrol... that would be great for defence.
Now, would the Ai use it? That is also a question... if Ai fears surprise attacks maybe yes... it could make Ai better at dealing with Human players guerrilla tactics??? It's a bet...
I would allow 2Upt optionally also, or allow mini armies of three different units to combine into a single one, without commander....
Then make a commander promotion to make him move up to six 3x units armies in a line or wedge formation, or just all of you units now will follow him, and stack up to 6x tile and then on a line.. sort of select all units of the old SoD times.... it would make thousands of people's life easier