back on the subject of offensive bonuses (tile attacked from and tile attacking into)..
Here are some thoughts:
forest defense bonus? why? the legions didn't exactly climb on trees into perfect defensive positions when attacked at teutonberg forest.
And as it is, it buggers up elf civz because they cant drive away attackers.
I reckon offensive bonuses are much more interesting than defensive bonuses, so the forest defensive bonus can be removed.
The hill one should stay because it makes sense.
running uphill tires people.
now:
1) elven melee and archer units should have a 20% bonus attacking into forest, a 10% bonus attacking FROM a forest (can be combined to 30%), and 20% defending a forest tile.
2) Cavalry units should have a +20% bonus attacking into plains, +10% attacking FROM plains.
They should also have -50% to offense when attacking into forests or jungles.
(this is best uniquely assigned to cavalry because it makes sense with cavalry while making no sense with say, axemen.. unless of course its unique cavalry

like some.. I dunno, giant ****atoo cavalry).
3) Dwarven units could get an extra 20% bonus when defending cities, helping flesh out their 'stalward defender' style (if indeed you're going for standard fantasy dwarf style).
4) this is a bit of a headache, but cavalry units, I think, should be able to retreat loki style from attacking melee units when defending plains or hill tiles. hard to implement though?
5) Golems should have +50% attacking hills (negating the hill defense bonus) and perhaps +10% to attacking into forests and jungles.
Because golems don't get tired running uphill.
Nor do they have any problems with snagging branches and biting insects.
6) undead units should have no attack penalty when crossing rivers (they can just walk over the bottom), and they should also have a +50% attacking into hills, thus negating the hill defense bonus, again, because they suffer no fatigue.
There is so much more that can be done with offensive combat bonuses.. desert and tundra civz could have large bonuses that actually mean something on their home terrain, able to drive attackers away instead of sitting and defending and hoping the enemy won't pillage instead of attacking the defending stack.
Unique units could get unique bonuses that are another step in flavour and tactical differentiation, etc.
of course, it has to be possible to implement first :>
Unrelated but also nice:
Amurite firebows should, instead of fire II promotion, should have access to simply an automated effect that creates a fireball whenever an enemy is within fireball range (3 tiles?).
then you'll have to click a lot less and not get them out of fortify mode. I mean, you have no reason not to summon that fireball (which isn't that strong anyhow), so best if its automated.