Whenever one thinks of something new to introduce to war I always think: Yeah. They were smarter than you and more experienced. They had the ability to think of your basic idea and did not. Probably for a reason. But I'm curious to actually find out.
Lets imagine a portable watchtower that can be constructed in the field. Height is about 15 meters. And it has wheels. With the sole purpose of having a soldier on top to surveying the battlefield and report back to people below who in turn would inform the general of what is going on.
The setting in question, this can be very general, already uses signals and banners...etc to identify units so a watcher on top should get more information if surveying from a height of 15 meters. Anyway the tech is roughly 16 century. Nothing more.
I think you all know the problems of dust clouds or failure to recognize friendlies coming up from a direction and thinking them hostiles...etc
Obviously we know from history that even siege towers were made, it took more time but they need to be armored and this does not, and that they were even mobile. So. The ability to make it is not impossible. So. It's a question of is that a good idea not if it could be done.
Is this a good idea that adds value to the force in question? Why? Not a good idea? Why not?
Edit: As requested to specify the usage of them. I thought it would be a little general. Basically I imagined that the material of making them would be part of the baggage train so that a commander would make one if he thinks it would help.
Obviously if he sent a cavalry detachment to ambush the enemy or if the battle is a seaborne landing then again that is not useful. So. It only becomes a tool for the general.
Example. The two sides are already engaged in melee. Then the commander, from the back as it is usually done, to make the tower. The tower is quickly erected and manned. Then maybe the watcher sees an week section or can see reinforcements coming to a section of the enemy's line...etc.