In an Independent state there is just 1 armed force and it answers directly to the government it is not an independent melitia. Hezbollah were created during a war and they don't want to disband but the national government doesn't have the capability to forcibly disarm them so is trying to find a compromise. Hamas wants from the start to have a right to this independent military capability. What are they going to do if by some miracle the talks do restart and Israel insists any palestinians state must be fully demilitarised? Fact is if Hamas want to be part the government but want their own official force then The entire PA will be held responsible. It won't be Israel v Hamas it will be Israel v PA because Fatah make themselves equally as accountable as Hamas and must face the consequences equally.
Sunni Arab nations are 'Israel's allies,' says Israeli Foreign Ministry director general (JTA)
from the article: Hamas wants to employ the 'Hezbollah model'