Hi!
I think pricing range benefits from 5cm upwards is a good idea. Using the base range of 50cm may be giving too much of a discount to ranges as a whole. So I like the idea to tackle that particular aspect.
The problem I see with template weapons is that a barrage template is more valuable because there is a high range attached to it. In other words, those templates do not originate from the firing model in the sense that the template touches said model for its effect. In case of most artillery there is a long range then the template is placed.
In this scenario it is proper to cost in a high fashion the template size, since its ability to "travel" a long distance that makes the barrage template valuable (thus bigger is very much more useful than smaller).
However, templates that do originate directly from the model (the template touches the model and the effect starts from there) are VASTLY less useful than the typical artillery barrage because in this scenario the range IS the template.
This means the template cannot span a ranged difference like a standard barrage does and is limited by the models move and templates length to exercise its effect.
I contend that templates in this later scenario cannot be priced with the same weight as templates in the first scenario, since stat by weapon stat a template that can span a range and then apply its effect is much more valuable than a template limited by its own dimensions and model move.
Expressed in other terms, two templates of same size, same BP/attack dice, to hit and TSM, where one has a range to travel before it lands should cost much more than that very same template with identical stats that has to be placed touching the firing model and only be able to effect within the area of the template itself.
These two cannot only not cost close to each other, but the one with a range attached should be worth some multiples more than the one without.
While area covered by the template is important, its the ability to "throw" that area under the template via range that makes the template size valuable.
Those that can't do this are markedly less valuable since their worth solely resides in size and stats because the "range" is the template itself.
I'm not sure where to inject such a modifier to reflect this (or for that matter discount), but I believe that a more stark mathematical difference between the two needs to be formulated.
Maybe costing templates by their raw stats and area (like its done now) and then applying a multiplier by range (those whose range is the template could be "0.25" or some fraction like that) is one way of doing it, since the farther the template can travel the more valuable it is per size.
I hope that made sense.
Primarch