-- gamma scalping is also known as hedging your delta

it's coincidental that the structure (straddle) starts out delta-flat(ish), otherwise you'd be trading delta against it at the inception of the trade
-- there is nothing "defensive" about delta-hedging - it's a way to transform your risk from exposure to terminal distribution to exposure to realized volatility
-- all of the major Asian indices have high amount of structured product issuance, so the there are fair number of interesting things to do there (KOSPI and NKY are my bread and butter)
-- as a retail trader (unless you have portfolio margin) your capital efficiency as a delta hedger will be dismal, since you will be posting high margin for the stock
-- how delta hedge really depends on your risk preference - you can re-balance the book based on delta threshold, time threshold or a combination of the two. There are arguments for either
-- another parameter that most people ignore when hedging delta is what vol to use for hedging as it will determine your relationship with the underlying (e.g. in case of straddles if you hoping for mean reversion, you want to hedge at lower IV, while if you are hoping for a trend you want to hedge at higher IV)