A quick solution would be to simply add an Arial fontset. Just download
this, copy it to the folder: "C:\Users\
YOURUSERNAME\AppData\Roaming\XBMC\addons\skin.aeonmq5\720p\", and replace the existing file. Now open XBMC, go to "Settings -> Appearance -> Skin -> Font", and select "Arial". You should keep a copy of my Font.xml file, because whenever the skin gets updated this file would be overwritten, so you'd have to replace it again.
That was the easy way. The hard way requires you finding fonts that contain such characters, renaming them accordingly, and copying them over to the "skin.aeonmq5\fonts" folder, replacing the existing ones.
P.S.: Regarding the first method, you could do some meddling of your one to make the fonts more to your liking. If you open the new Font.xml you'll see it contains two fontsets rather than only one in the original. These fontsets start with these (lines 4 and 195 respectively):
Code:
<fontset id="Default" unicode="true">
and
Code:
<fontset id="Arial" unicode="true">
Obviously the second one ("Arial") is the one I added. If you believe there is no need for, let's say, the main menu font to be changed, find the corresponding fonts in "Arial" and replace them with the ones in the "Default". Specifically, for the Main Menu fonts you should look for the ones that have sizes of "50" and "60" (search for all the occurrences of "menu principal modelo"), and replace "arial.ttf" with "aeon_mainmenu
X.ttf", "
X" being the number of the font.