Answer
There is a distinct advantage to using + and - instead of other types of annotations, because of the arithmetical nature of zero net charge, when there are equal amounts of both types of charge.
There are no significant consequences in changing the signs.
Work Step by Step
Charge comes in quantized amounts that are always integer multiples of $e$.
The current convention is as stated in the text: electrons are awarded the negative charge, protons the positive. There is a distinct advantage to using + and - instead of other types of annotations, because of the arithmetical nature of zero net charge, when there are equal amounts of both types of charge.
It would take additional rules and procedures to acknowledge that, say
cA+cB = zero charge.
As far as the assignment of negative charge to the electron, Coulomb's Law states:
Electric charges exert forces on one another along the line connecting them:
Like charges repel, opposite charges attract.
(How we annotate them has no real bearing on the law)
The magnitude of force is $F =k\displaystyle \frac{|q_{1}||q_{2}|}{r^{2}}$ ,
and will remain the same if we swapped the + and - on the types of charges of $q_{1}$ and $q_{2}.$
As pointed out, the important piece of information is that they of the same type or not. So, there are no significant consequences in changing the signs.
Also, the magnitude of the electric field caused by a point charge is: $\mathrm{E} =k\displaystyle \frac{|q|}{r^{2}}$ .
The directions are a matter of convention. The convention used is that
$\vec{\mathrm{E}}$ points in the direction of the force experienced by a positive test charge.
Changing the convention to "... experienced by the negative charge," would not have significant consequences, except that the arrows would point the other way around.
