No permit dude for a major reno is just asking for major headache. Seriously not worth the headache and pocket pain you will feel.
Not all bandaraya fellas accept Kopi 'O' anymore and in the worst case scenario, besides a stop work order, the council can also get issued a case against you if the renovation is extensive.

Lets put it this way... If you're willing to fork out 5 figures in the event that you're caught, the go ahead.
The amount to spend is for submission of plans, architect fees and of course a nice hefty compound summons. My friend had the unfortunate experience where he had to fork out almost RM20k to get all necessary approvals and to settle a reno that was never approved.

Usually takes a year + at the fastest to get this sort of approval. The plans submitted will have to be from an engineer and must be complete with new pillars to bear additional load, ground footings, ground & ceiling beams, etc... The whole process would easily set you back RM15k just for the approvals.

Saw one house in TTDI, approval only received 2 years after initial submission.

No you won't. Don't worry.