I don't like the 3 missions caps you want to implement but I understand it may be too much for new players. My suggestion is simple. For combat missions:
- Harmless: 3 missions
- Mostly Harmless: 4
- Novice: 5
- Competent: 7
- Expert: 9
- Master: 11
- Dangerous: 14
- Deadly: 17
- Elite: 20
The same for Trade and Exploration missions with its respective ranks.
- Harmless: 3 missions
- Mostly Harmless: 4
- Novice: 5
- Competent: 7
- Expert: 9
- Master: 11
- Dangerous: 14
- Deadly: 17
- Elite: 20
The same for Trade and Exploration missions with its respective ranks.