1- This person must worship Allah the way Allah wants not the way He wants. If we worship Allah the way we want then we are worshipping our desires. Allah clearly commanded us to pray and He considers it a big sin if we don’t. We must respect that and follow that. Yes Allah is merciful but it doesn’t mean we violate his laws. That’s like someone says “I know my government is so loving so I will break the laws and not pay tax and do illegal things.” Is this acceptable by rational people?
2- Allah may choose to forgive it He wants to. However, when we don’t pray, one outcome could be losing our faith at the moment of death. Prayer protects us from shaytan and evil at the moment of death. It protects us in the grave and on the Day of Judgment. So without such protection, we can be pulled by Shaytan, lose faith, and yes consequently the person may end up in hell. Is it worth taking such a risk?
Also, why is this person so bothered by prayer? If Allah is so loving and he loves Allah, what’s the problem if he stands for a few minutes, speaks to Allah and shows his humbleness before Him? Why doesn’t he follow the Prophet (s)? Did the Prophet ever say, “Hey, God is so loving it’s ok if you don’t pray?” Is this person making up his own rules and laws or does he genuinely want to follow what Qur’an and the Prophet say?