Time decay of leveraged ETFs depends on volatility and the price "path". In brief but strong directional moves, or in a gradual non-volatile price change over time - one may see the inverse effect. Shorting inverse ETFs (instead of buying a long ETF) can work to your advantage when your trades are in the right direction, but losses could be larger if trade direction is wrong.

As for writing naked calls: "Risk factors of shorting naked calls aside... makes sense" . A strategy of writing options does not make sense if one puts aside risk factors; the whole idea of the trade is exchanging risk with option premium. Systematic options writing on an index might yield many small gains, with occasional big losses that could easily wipe the gains (imagine that naked call trade if the market were to move in the other direction). For such a strategy to work one needs to very well understand the risks as well as rewards, and there is no free money here. Writing options on a leveraged or inverse ETF combines two leveraged tools with non-trivial behaviour - a very risky proposition if one does not understand them both very well.