Reckon JS has hit the nail on the head with the grant system or some variation of it being the best way to deal with option packs that are genuinely required to make a car suitable.
The manufactures are in the business of selling cars to make a profit and forcing them to give away or heavily discount option packs runs the risk of them leaving the scheme due to reduced profits.
Creating a “Motability spec” specific model is probably very costly from a production line perspective and may end up reducing the range of standard models available or end up being a compromised spec where some features have been removed / replaced, for example rear view camera added but satnav deleted to even out the cost.
Its a shame really that manufactures are going down the option pack route as it more or less forces people to pay for stuff they don’t want / need in order to get the bits they do… The cynic in me wonders if its a way of temping people in by having an attractive sticker price knowing full well that many will buy option packs in order to make up for the “missing” bits that should have been included for a given spec.