GoodSmile will use your feedback to decide future figure productions but cant make any guarantees. If there are a lot of requests for a particular character then the more chances it has for PVC-ification.
Also, if you have a fave illustrator like Shunya Yamashita, Itou Noizi, Tony Taka, Ino, Pink Chu Chu etc then let us know too.
Figure makers have more freedom when working with illustrators due to not having to pay license fees for the likes of Haruhi etc. They also have more freedom and dont need to obtain permission to sell figures in certain markets. For example, if Goodsmile want to officially release a Haruhi figure in the US, they need to get permission from the official licence holder in the US (which is different from Japan). All these licensing processes and paperwork just adds time needed to release a figure.