Ren'py won't work with NLT's style.
To match up with his 2 weeks schedule he'll have to produce A LOT more content than he does now for RPGM.
The main plus point of using RPGM is the free roaming, the puzzles etc, they add to the playtime.
RPGM is perfect for his 2week update schedule.
If he decides to switch to Ren'py, he'll have to change his schedule (1-2 months per release at least
)
Switching to Ren'py will do more harm than good.
Other options like Unity are better. But i don't know if all RPGM features like free roam/puzzles etc can be replicated in Unity