I have entertained and checked the position of Ord Mantell several times. This is why I drew the compass lines on the map because it is the definitive way to settle the whole issue of Ord Mantell's position. Now I can rationalise why it makes sense for Ord Mantell until I'm blue in the face but some people won't listen to reason, so in that situation I fall back to basics. Ord Mantell, on every single galactic map, has to be somewhere north of the core worlds. Now if Dantooine is a world which appears in the game, and assuming from the web-comic it is, then it is possible to draw a line from Tython to Dantooine and somewhere along that line it passes near to Ord Mantell.
Now I might be slamming my head against a brick wall here but I think it is only fair to fully evaluate someone elses opinion when it differs from my own. I never assume people are idiots, there is always a reason why someone forms an opinion and the goal of any discussion which involves trying to bring someone around to seeing and agreeing with another perspective is addressing the root of that opinion.
Since this image...

... comes from Bioware just like the timeline map we will first plot out the known planets so we have a frame of reference.

Now that places all the worlds in the right place according to the compass. First, lets add the compass to a galactic map. Much like I did with my map I've made the compass fit the planetary position from the composite I first mentioned rather than drawing a line through the middle of the galaxy.
You can find the link to that image here.With these new lines drawn you do have clear benefits, Manaan now appears in the position of one of the markers east of Aderaan. But in the process you lose Dathomir from my theory map.

There are clear benefits from spinning the directions around so that Ord Mantell is in Republic space. However in order to do this you need to remove Ilum and replace it with Kalee which was general grevious' homeworld. The reason for this is that Ilum is due west from Ord Mantell but the marker is clearly north-west. Therefore the only planet of any significance there is Kalee. Korriban has to be the furthest marker from the east compass line. Nal hutta needs to be due south of Korriban in the south-eastern region. The line from Nal Hutta to Alderaan passes by only one significant planet, Manaan. But the problem with this is that the planet is completely covered with water and in the prologue for TOR it says that the Selkath have retreated under the ocean. Most of the problems then occour when dealing with this south-eastern region. Kamino is in the right place but it seems odd that yet another water world is included, but it is at least a famous planet. This marker might also be the Bothan homeworld. The marker further out from that Kamino/Bothowui marker could be a number of obscure worlds, the only one with any Sith/Imperial connections is Pzob.
On the Republic side of the border we have some encouraging possibilities. Mustafar is in the right place, Utapu is and the marker for Tatooine/Geonosis is still present. Then we come to the south-western region... Phu. Yes, Phu. And trust me on this, it couldn't be anything else. On the galactic map that area is almost completely devoid of any worlds and the only one which is around half way up from Geonosis and the inner core is Phu. The planet is largely unknown and only gets a passing mention in the Boba Fett novels. The planet was also included in the first draft of the Phantom Menace so it was planned to be in the films at one point.
Is this map possible? Of course it is. There isn't any glaring inconsistancies in the markers from known planets but what it does remove is a number of worlds which have been loudly hinted at by Bioware. Ilum and Dathomir are mentioned by name in the history prologue along with the mention of Selkath retreating underwater. The web-comic also suggests Dantooine will be in-game but it would be impossible to get Dantooine onto this map because it needs to be directly north of Ord Mantell along the northern compass line.
The theory that Ord Mantell is within Republic space is certainly rooted within a solid theory. It does allow for a number of planets which are famous but I personally feel it excludes more than it contributes. I suppose we'll have to wait to see what the next couple official worlds will be.