Increasable and decreasable signal strengths - Minecraft

I have found a viable solution: Signal strength memory

It does exactly what the description says, except the "button" has to be exactly 2 ticks or it will increase/decrease too much. A simple pulse shortener should sort that out.

Here is what it looks like as well as a layer breakdown:

Maybe you could have two droppers facing each other and get a signal from one with a comparator, one button could cause a dropper to add a item to the other and increase the signal strength and the other dropper could send an item back to the other to decrease signal strength.