It's been a while since I've been on WF4 and I don't have access to it right now but in Creo 2.0 here's how you do it (image below)...perhaps they are similar. Also helps to turn on grid and grid snapping.
Another method would be to create a new top level assembly and assemble the top level asm and your sub asm into it. Then you have control over simplified reps, etc. and it will always update correctly so long as you assemble them the same in both top level models...perhaps via a skeleton or other universal references. Since you are completely containing the top level assembly it will always be up to date and shouldn't ever go out of sync. I've heard this technique called "working assembly" or a "master view assembly".
With this approach you might run into problems if you are doing a BOM and need balloons to point to other views that use different models. Additionally you may have to filter out the top level assembly in any BOM list.
I have a similar requirement for exploded views and use the origin method. I am using shaded exploded views with extension lines and in drawings, those extension lines are not properly hidden behind solid bodies. So I create a shaded exploded view and have to align it to a no-hidden line exploded view -with- the extension lines (which hide just fine). These views don't always have the same centers due to the extension lines. I pick a feature to set the view center in each view and place it at a specific location on the drawing. As long as the feature I assign remains stable, both views remain in sync.
The problem I have with alignment is that it only aligns in vertical -or- horizontal. I can't seem to lock the views together.
There is another advantage to using the explicit coordinates for location... if you need to move one view temporarily for whatever reason, you can just change one of the coordinate locations for a time and move it back later.
Note: if the extension lines are outside the main geometry, the view's center is different than without the extension lines. Using a feature as a center will make the view center remain stable through changes making view management much simpler. From experience in a dynamic system library, locking views with a reliable and specific view center feature makes drawings much more stable. Likewise, views with alignment characteristics will remain more stable, but they normally still have one degree of freedom remaining.
