The 21-year-old also has his sights on a silver medal in the 50m backstroke.
He said he had been training hard and improved his backstroke significantly since Beijing.
To qualify for the London Paralympics, Leslie will have to prove himself at selection rounds in Hamilton during February, then in Sheffield, England.
Securing a certain number of achievement-based points in the April races at Sheffield will win him a place at the Paralympics, which open on August 29.
After a month back at home in Whangarei, Leslie will crack into his training regime from next week.
The athlete deliberately planned to have most of his Comms degree finished by this time, after starting it in 2008.
"It's business time this year," he said.
After swimming at the Paralympics in August, Leslie wants to focus primarily on wheelchair rugby, which he took up five years ago.
Originally part of New Zealand's national wheelchair rugby team team, the Wheel Blacks, he was undeterred by their failure in South Korea to qualify for entry into the Paralympics.
"It's simplified my year," he joked.
Leslie hopes to pick up a contract to play in the US next year.
He has not ruled out the possibility of returning to competitive swimming later in life.
Due to the nature of sport for the disabled, it is not uncommon for competitors with higher-level disabilities to enter competition at older ages than is usual for Olympic athletes.
The swimmer who ranked second behind the Whangarei athlete at Beijing was in his 40s, and had physical impediments which were "freakishly similar" to his own quadruple limb deficiency, said Leslie.
Grouped at level five, Leslie falls in the middle of the official Paralympics disability scale. The scale ranks competitors from most severely disabled, at one, through to those with more minor impediments, at 10.
Level 10 competitors tended to be relatively young, but more impaired Paralympians were often older.
Overcoming societal expectations, which could limit people with disabilities, was more difficult when those disabilities were visible to the public.
In the supportive Paralympics environment, returning to competition in his 30s as an "old guy" would not be unusual, he said.