The move would see a reversal of the numbers worn by Johnson and Leuluai last season, and regardless of whether he wears the six or seven, Johnson said his roaming attacking role would not change.
"Tommy was wearing number six and I was wearing number seven and he was the halfback of the side, really," he said of their 2014 halves partnership.
"He was pushing the boys around the park and I was just sort of floating.
"At the moment we've got a good balance where I'm on the ball trying to get us around the park but as soon as something happens I'm straight off that and into running.
"So I don't see why we have to change that but if he wants to then I'm not going to stand in his way."
Ahead of his milestone match, Johnson acknowledged the influence McFadden has had on improving and developing his play, since replacing former head coach Matt Elliott early last season.
McFadden has designed structures for both he and current five-eighth Chad Townsend to operate within, and although both halves share the organising duties, Johnson still has the freedom to play his natural game.
"He's [McFadden] helped massively. The style of plan that he's put together for our side to play, it allows me to play my own game within that.
"I'm a player who likes to play off instinct and opportunity and he hasn't set any hard structures around what I do.
"We've got forwards that are really rolling forward and creating us that second-phase footy and I'm just jumping on the back of it.
"It's a pretty simple method but these are the games coming up where we're really going to get tested and our game model is really going to have to stand up."
Sunday's away clash against the third-placed Roosters - the best defensive side in the NRL - looms as the biggest test of the season to date for the fourth-ranked Warriors.
Both Johnson and captain Simon Mannering were given an early reprieve from yesterday's training but are in no doubt to play at Allianz Stadium, but interchange front-rower Charlie Gubb will have to prove his fitness after a head knock forced him off against the Storm.
The Warriors are already resigned to being without Konrad Hurrell (shoulder) and Manu Vatuvei (shoulder) for the Roosters clash, although both players completed training yesterday.
Back-rower Ryan Hoffman also did some light running as he continues to recover from a calf injury suffered in last week's State of Origin decider.