yes, if it is possible to make units that only collide with weapons on not with projectiles so that units can still drive over the spice.
But in that case I would do it different:
have an array
spice [x][y]
it stores how much spice is on the ground at each map coordinate.
the spice is drawn with Lua.
If a harvester runs over the spice at [x][y]:
spice[x][y]--
harvesterCargo++

drawing and reading [x][y] would work similiar as described in this thread: viewtopic.php?f=23&t=24820

instead of red you would draw a "spice texture" and instead of green you would draw nothing.

Looking at their map design this approach is probally better as they have "fields" of resources. Conflict Terra has small "clusters" of resources, like Starcraft, age of empires etc.

not sure if you want the "building on sand requires to make concrete plates" like in the original dune?
that would be possible in a similiar way.

afaik they don't want any buildings on sand, only on the rocks (stable areas).

But what if ground decal is off?

Gadget with sendcommand grounddecals 1

The dunes look way more pronounced than they actually are, texture is just a placeholder of course.

dont some players turn off grounddecals for a reason?
that would be like forcing gl pointsize (or whats the function) on ati cards.

oh, a nice map appears.

couldnt you use a different texture over the areas that are stable?

Yeah, use some grey earth like in Dune2!

I don't know, I've never heard of any problems with decals, so I'd think people turn them off to just run the game a little bit faster. Which isn't worth it if the decals contain important info.

it used to cause horrible problems not that long time ago. maybe ppl still remember that, but i dont really know what makes u think that 'some players' turn grounddecals off (btw, isnt it turned off by default?)

thats what i meant. They currently work good for me too.
still i think there are better ways to draw on the map then using ground decals. (see previous posts)
That is just one details anyway, first there needs to be one dune model ingame...