Without available mod dependencies the simplest way to access a mod is to have access to its mod folder root.
So my suggestion is the ability to define a reference name for the mod's root folder in mod.txt. It would look something like this:
Root = "MyMod"
MyMod could be the mod's ID but perhaps in line with ./Data it being ./CustomMod would be easier to implement and use.
With this by using MyMod for example "MyMod/Strings/en.txt" other mods could access the mod's resources.
Another problem I've encountered is the inability to use the reference in pathing like this:
DamageLevels
[
{
File = "Root/thrusters/floor.png"
Size = [2, 1]
}
]
// or
AnimationFiles
[
"MySource/weapons/barrels_2.png"
]
// or
Texture
{
File = "MyButtons/On.png"
MipLevels = 2
SampleMode = Linear
}
// or
<Root/roof2.txt>
So there needs to be a way to combine the reference which could be complex and specifically expand it in the actual path locally needed.
File = MySource + "weapons/barrels_2.png"
This is frankly quite important as it allows mod parts to be physically moved without messing up all the paths, therefore, reducing maintenance work and errors.