Is it advisable to approve my sister's marriage to a man who does not show signs of commitment to the Prophetic Sunnah and is negligent in performing prayers in the mosque after his return from Saudi Arabia, despite his maintaining them during his stay there?

If the suitor performs Hajj, prays, and fasts, then there is good in him, and his shortcomings regarding shaving his beard and being late for congregational prayers can be addressed through advice and explaining the Shariah rulings to him. However, if he delays prayers until their time expires, he has committed a grave sin, and no good can be expected from him until he straightens himself out and draws closer to Allah.