I was going to wait with posting this untill I had finsihed it, but since it seems I will never finish it, Ill just post the unfinished thoughts and bits now.
Maybe I'll get some inspiration to make some example weapons and to fine tune it later on.
Summary:
1. Divide all weapon types into size categories.
2. Speed, damage and special limitations for each size category.
3. Weapon specials.
4. Energy weapon template.
5. Heavy weapons template.
6. Attack rating and damage.