We don't really need custom formations, we just need a few formations which are useful.
The problems I see with the current formations are that:
1. There are currenly only two rectangular formations, "Line" and "Box";
2. These formations do not allow for the positioning of different tech levels;
3. That when different tech levels of naval vessels are grouped together, the formation will expand too far.
I would recommend that formations be expanded to include "Chevron" and "Circle" formations. I would also recommend that these formations contain some variety on priority within the formation. Or instance, having a "Heavy Lead" and "Light Lead" formations which would put all the heavy units to the front or the rear of the formation. As well options for a "Heavy Center" formation. Which would put the higher tech units to the center of the formation, with a perimeter of lighter units surrounding them.
I would envisage the most useful formations would look something like the following:
Line - The default rectangular formation with a higher width to depth aspect ratio. Heavy lead main battle line formation.
Box - A defensive rectangular formation with equal width to depth aspect ratio (ie. square). Heavy units are placed around the entire perimeter.
Chevron - A modified "V" shape assault formation. With Heavy units placed on the leading edges of the chevron.
Circle - This is a light unit defensive formation. Where a vunerable High tech unit is surrounded by a picket line of smaller units. This is a light lead formation.
I also think that the spacing of different tech levels in naval formations need to be reworked. Such that the T3 vessels are given a larger spacing, and the T1/T2 vessels given a smaller spacing. With the two matricies coinciding. As it currently stands, mixed tech naval formations are unwieldy, and unworkable.The only way I can effectively operate my navies is to have my T2 escorts in an entierly separate group.