Guides for aiding centring/aligning camera with square on items in frame with 3d perspective

I regularly have to shoot product shots and of course normally a range of angles of each product. Quite often there will multiple products in a range or different colours of the same product to cover so lots of duplication of shots and angles and switching the products around in set.

One of the frustrating aspects of this kind of shoot (particularly for boxy rectangular shape products) is straight head on shots which show the depth of the product so a square on front showing some of the top too. Here the perspective of each side edge running front to back has to be the same so you have to be aligned exactly centred on the product and dead flat square on. While keystone corrections can square up the front panel, if you're even very slightly off square it cannot correct the side edge angles on the visible top (if you're not centred even by a tiny amount one side edge will have a straighter or more acute front to back angle than the other side). Rotating through multiple versions of products can consume a lot of time getting the alignment and 3D perspective spot on and consistent. 

The existing C1 guides can help with this to a certain extent but what would really be amazingly useful is a specific guide for centring. This could work by having a fixed, and centred on a choice of crop or frame, horizontal and vertical guide from which you can pull out another guide (ideally two sets in each orientation, different colours for each set?) which would have an automatically reciprocated equidistant guide in the opposite direction thereby allowing an easy accurate comparison of certain points on the product from side to side or top to bottom relative to the centre which would be a very quick way to check this kind of perspective alignment and aid positioning in set. This  can't be corrected without individual image post production. 

It sounds a simple kind of thing to shoot but actually can be quite time consuming to get the alignment right in my experience. Aside from studio work I can see a use for this in interiors and architectural work and in fact anything where there is a 3d view of an object or situation and the camera position must be centred on it.

Yes