The answer is: yes, a possibility for simple, freehand doodling tool is a good idea, both for the schmeppy concept in general as well as productivity/creativity. A set of icons are also possible though complicated. A combination of the two would be an abhorrence. Below is explained why.
Taking it from an angle of psychology and linguistics, long and fancy words that actually boils down to: I see something from top view, a squiggly blob filled with green colour (perception). I associate it directly with what it represents, without having to read or figure something out - a tree. (association, representation, intuitive design, cognitive load/strain)
The goal: With as little information (like in data) as possible the sender (gm) should invoke the idea/representation the sender has, as close as possible in the receiver (player). This falls into the concept of schmeppy if you ask me: simplicity. Less ‘fuzz’, attention won’t wander around, it is down-to-business from the first moment when eyes are laid on the scene. Just as schmeppy is to a large extent today.
If I prep a scene and want to do a tree or shrubbery in schmeppy today I find that scale forces me to use alot of squares, hence making large overview maps unwieldy. I also use 2-3 shades of green and fiddle around w borders for the player to understand that it is a shrubbery or tree without having to ask what it is. Still, the player says it took quite a while to figure out. If I have to mark it up with a token the work is actually forfeit, but also the representation of the ‘world’ that the map is, limps. Some things are written, some things intuitive, some things takes explicit figuring out (reasoning) - different dimensions increase the constant cognitive strain. In other words: fuzz and attention stealing features is introduced and the receiver spends more cognitive effort on understanding the map rather than putting that effort into playing. A small, freehand, green doodle eliminates this. A small diversion from the graphic representation concept of schmeppy makes a grand increase in the basic tenet of simplicity.
There are two middle roads though
1 - diagonal borders for mimicking ‘round’ shapes. This will cut back the scaling issue considerably
2 - set up a battery of ‘icons/symbols’. For example a scale-to-size ‘tree-icon’ and a ‘shrubbery-icon’ that can be plotted overlapping to mimic a hedge.
The icon solution takes a lot of effort designing icons making them intuitive and scalable. From an on-the-fly map creating perspective the freehand is always faster. Both? Now complexity really takes off and schmeppy is lost.