Before 16w38a, Passengers of an AS with Marker-tag set to true were at the BOTTOM of the AS (the AS was stuck inside the Passenger, see pic with creeper as example).

Now Marker-true-AS got their Passengers at the top, which might mean huge problems for mapmakers who frequently use invisible Marker-AS with Passenger-entities for their maps or at least for some of their CB inventions/contraptions.

Apparently this is caused by Marker-true-AS also now having a hitbox, unlike before 16w38a, and apparently this hitbox was needed in order to fix other AS bugs.

Steps to reproduce
1. Summon as example a Creeper as Passenger of a Marker-AS:

/summon armor_stand ~ ~1 ~ {NoGravity:1b,Marker:1b,Passengers:[{id:"creeper",NoAI:1,Silent:1}]}

2. Look at it in e.g. 16w39c and 16w36a to see the difference very well.

As this could be a concern for mapmakers, please fix this BEFORE 1.11 OR add an alternative for 1.11, e.g. offset-possiblity or a designated new simple invisible marker entity (see Suggestions below).
If this gets fixed or reverted to its old state, please keep other fixes for AS that were already done or are currently in the making.

Screenshots attached.

Suggestions
I just read it again in the comments and heard it also by other mapmakers/CBers since longer:
A possible solution would be to give us an offset-possibility for Passenger-Entities on AS, preferrably also all the other entities, without having to use relative-tps or the likes.

This would maybe also start a change in the thinking of the CB community who still use AS due to them being the "old safe known method" and would maybe make them more comfortable in using alternatives like an AEC.

Another possibility could be to add a completely new Marker entity, a simple, invisible Marker.
The "workarounds" we use currently like Armor Stands and Area Effect Clouds do work, of course, but a real designated simple Marker entity would be great to have.

Sadly new implementations often need time (incl. testing+bugfixing), and apparently 1.11 is already feature-ready, which means a release could be near. That means either this bug will be fixed or gets resolved as "works as intended" before 1.11 release, and CBers will have to change their maps/inventions accordingly, or this bug will still be open after 1.11 release, and if in 1.11.x or 1.12 an offset-possibility and/or a new designated marker-entity will be added OR this bug here will be fixed, that'd possibly mean the CBers will have to change their maps/inventions yet again.

We can wait to change our commands and for fixes or new implementations as long as we know about when and that we will get them at all. But for the sake of the community and the Devs.it should be avoided, if possible, to have us everything changed for 1.11 and shortly after we'll have to change everything again.

It'd be really kind if Mojang could be a bit open in which direction they want to go, even if they currently don't have the time to fix or add anything before 1.11 release, so we can plan when or if to update commands related to this Marker:1-change at all.

Thank you!