More radical one
1. A long shot goal is counted as 2 points.
Not every goal is equal in term of quality. There are planety easy goals such as goalkeeps' howlers, some own goals, some goals after rebound... There are some difficult goals such as long shot goals. Basketball recognizes this difference. I think soccer should follow basketball, reward long shot with 2 points. How long deemed as long shot can be discussed. I favor adding 20 ft arch similar to basketball. Any goal outside this arch is a 2 point goal.
It will bring more comeback-victory dramas to the soccer game. It will change the parking bus strategy of leading team in last 10 minutes because you do have a chance to lose instead of just tie. As a result of strategy change, soccer game will be become more offense oriented throughout 90 minutes.
2. Reform penalty kick. People have talked about this issue for long time. It sucks when so many games were determined by soft and often very controversial penalty kick. It's unfair to hard-working players and fans. Again, not all fouls inside the box are equal. Some fouls are really soft. We need to distinct the penalties insider the box. My suggestion is we still reward 12-yard spot-kick penalty to those fouls which obviously would otherwise lead to score. For the soft fouls, we destinate 3 18-yard spots on left upper corner, center and right upper corner (all near the box line) for free kick and allowing only maxium 3 person wall for defenders. For example, if a soft foul occurs at left side of box, attacking team will have left upper corner free kick. Of course rest players except 3-person wall have to stay outside the box, just like 12-yard spot kick.
3. Widen goal by 2 inches each side and increase its height by 2 inches.
It's because players today are tall than those of 100+ years ago.
less radical one
3. No injury time substitution. This strategy may be ok in basketball game, but I think it's bad for soccer game.
4. Allow 5 substitutions each game.