French international referee Mathieu Raynal said on Tuesday he would like to see a time limit imposed on scrums and fewer replacements as he announced his retirement from rugby.
There is no law in place on the time allowed for a scrum and the set-piece can take more than a minute to complete.
Sides are allowed to use eight substitutes during a match.
Raynal will referee his 50th and final test match in July, becoming the 13th official to reach the landmark.
"There are two things I'd like to see to increase the ball in play time," Raynal told AFP.
"That we limit the time it takes to set a scrum to 30 seconds, that we put in a shot clock like for penalties and conversations.
"There are too many replacements that come onto the field in the second half, I feel it breaks up the flow of a match.
"I would be in favour of having more people on a team sheet, 30 players for example, but we limit the number of replacements to five or six per match," he added.
Raynal has taken charge of games at two Rugby World Cups, eight Six Nations, five Rugby Championships as well as two French Top 14 finals.
"I was lucky and had the privilege to referee at the highest level," he said.
"I gained the respect and trust of players and coaches and I didn't want to damage the respect they have in me by doing one or two years too many."
Raynal has recently opened a guest house with Perpignan winger Mathieu Acebes on the Mediterranean coast but he would also like to stay involved in the sport as an advisor.
"I have a lot of options. I can stay in rugby or leave it," Raynal said.
"My family is the referee family. If I can stay in refereeing, it is the option that would interest me the most.
"I think I have a lot to give to others, the younger generation," he added.