Setup a folder to contain individual alias files that can be easily created.

add-aliases.sh

#!/bin/bash

[[ ! -d ~/.bash_alias ]] && mkdir -p ~/.bash_alias

# path to individual alias files
APATH=~/.bash_alias
ALIASPATH=$APATH

AFILES=($APATH/*.sh)
ALIASFILES=$AFILES

# add alias files from ~/.bash_alias
if [ -e ${AFILES[0]} ];then
	for AFILE in $AFILES; do
	    source $AFILE
	done
fi

# isalias 'foo'
isalias() {
	if [ -e $APATH/$1.sh ]; then
		echo "Alias exists."; 
		return 0;
	else
		echo "Alias does not exist."; 
		return 1;
	fi
}

# command to EASILY add, replace, or append a new alias
# addalias "foo='ls'"
addalias() {
	# extract alias name
	aliasname=${1%=*}
	isalias $aliasname
	yesitis=$?
	addit=yes
	addto=no
	yn=N
	aliasfile=$APATH/$aliasname.sh
	# what happens if the alias file exists?
	if [[ $yesitis == 0 ]]; then
		read -p "Would you like to overwrite it? [y/N] " yn
	    if [[ $yn =~ [Yy] ]]; then
	    	addit=yes
	    else
			read -p "Would you like to append to the existing alias file '${aliasname}.sh'? [y/N] " yn
			if [[ $yn =~ [Yy] ]]; then
				addit=no
				addto=yes
			else
				echo "Choose a different name."
				addit=no
				addto=no
				return 1;
			fi
	    fi
	fi
	if [[ $addit == yes ]]; then
		echo "Creating alias file '${aliasname}.sh' in '${APATH}/'"
		echo "alias ${1}" > $aliasfile  && echo "Alias created." || echo "An error occurred."
	fi
	if [[ $addto == yes ]]; then
		echo "Appending to alias file '${aliasname}.sh' in '${APATH}/'"
		echo "# appended $(date)" >> $aliasfile
		echo "alias ${1}" >> $aliasfile && echo "Alias updated." || echo "An error occurred."
	fi
}