There's a big difference with the current startups/new owners in the Australian market compared to the budding airlines of past. They are backed by some serious money, Bonza has 777, Rex has PAG, plus it's original investors, Virgin has Bain. Whilst these may be savvy corporate entities that could shut down and break up each airline at a moments notice, they also have the staying power and foresight to keep pumping in capital if they see weakness in any of the competitors for a long haul profit. They would be betting on someone else failing so they can gain serious market share in the Australian domestic market. Any one of those 3 could disappear over night or keep fighting till the cows come home. Alliance is on it's own and was seeking to sell out to QF, what does that say, who knows, are they safe and stable, well, that's a guess at best for any long term bets. In the short term they are doing fine.
I'd take the conditions that offer the best outcome for you and your family, in the long run. Jumping between airlines can cost you seniority and income starting from the bottom each time. Being in a base you don't want to be just for a few extra dollars or a type endorsement can be heavy on the soul and the family. Worrying about whether your airline will be around in 5 years is not worth thinking about, even QF mainline will boot you out in the cold if you are bottom of the seniority list when down times come around, so it's not just about who will go bust.