As we all know by now every plane has a different stop position because not all planes are the same. This causes profile devs to choose the aircraft they own or the most common one for that gate to base the stop position on which works for that one plane but not the 10 + other planes.
I suggest reading the chapter in the GSX manual named "Understanding the Stop position", because that's not how GSX ever worked.
The airplane which was used to customize a profile doesn't really matter, because
when a custom Stop position is set ( something a proper GSX profile should always set, it's the first thing I usually do when starting a profile ), if the airplane used by users is not the same as the one used by the profile creator, it won't matter, because what will happen instead, is that GSX will place the
Preferred Exit of the user airplane in the same place as the
Preferred Exit of the airplane which was used when the profile was made.
Which is what you want, because when you have the main exit always ending in a predictable place, you can be reasonably sure that, if the jetway worked with the airplane used for making the profile, it will likely work with any airplane, barring large difference in heights, where the jetway is not really designed to work across a wide range of door's height. So yes, you might still want to be in the same *general* ballpark of airplane class (don't use a CRJ to customize an Heavy gate), but with the main exit always in the same place, in conjunction with the TEST function (NumPad5 while editing the Parking), it's not really an issue having to be sure the airplane is exactly the same.
Of course, precisely because the relationship with the front gear and the main exit is different for each airplane type, the result of having GSX positioning the airplane with the Exit in the same position regardless of the airplane used, will
automatically result in the front Gear ending up on different stopping positions, exactly as it should be.
The thing is, many users ( and profile creators too, seen on many tutorials ) seems to always focus on the front gear, assuming they set the "correct" position, when in fact they are only setting a "correct" position for that single airplane model they are using to customize, when they should have focused on the Preferred Exit position instead, adjusting it for the best jetway solving position, and don't mind the front gear, which WILL change depending on the airplane model. That's also why GSX shows a dashed indicator that extends out of the Exit, to help align it in relationship to the Jetway, to further point out what really matters is the Exit, not the Gear.
Also, a common mistake I often saw on some tutorials, is the Stop position is not changed, because sometimes it already "looks right", so they creators don't bother changing it. That really means NO Stop position is set, so GSX will revert to the default positioning method ( center of the airplane in the center of the parking + an extra offset to compensate for large parking spots ), which doesn't do all that Stop position vs Exit compensation. Even if the Stop position looks right when is not customized, it SHOULD be moved, if ever so slightly, just to be sure it IS customized.
A way to know if something in the editor is customized, is to look for an Exclamation point over the object pointer. If there's an exclamation point (which will jump up/down when the object is selected ), it means that object position is NOT default anymore, so it's customized in the profile. This is valid for any objects, vehicles and the Stop position.
Are there any plans to support multiple stop positions?
GSX already supports multiple stop positions by airplane, which are treated as an EXTRA compensation, in addition to the previously discussed one that places the Main Exit always in the same place when a custom Stop is set. We have been using it in some of our sceneries since a long time. However, it's not editable by users, because the way it's done internally, is that a custom routine can be associated to a parking spot, which will return different stop offsets depending on the airplane model. So, it's not easy to adapt to something with an UI, being a purely programming thing.
However, we might still want to allow something like this to be opened to user customization (which will of course make airport customizations way more complex), but for completely different reasons. Not because GSX can't handle different airplane types used in customization vs actual use, since it already can (if the a Stop is set), but because it's not a given this strategy would always match what you find in 3rd party sceneries that might use custom ground markings that can change depending on the airport, some using many positions, some using only 2-3 groups, and their distances might not always match the GSX method of "always get the main exit there".
So yes, it's something planned for a future upgrade, we only need to think the best possible way to make it as flexible as possible because, in theory, it should be allowed to set a different "table" of custom offsets for each parking.