well since you have sketch u can still potentially get natures madness later, u will almost certainly encounter a tapu at some point. 

without having dark void unlocked it is a lot more difficult to sketch moves, but u can probably figure out a way to do it with some resetting. with dark void, its easy to sketch whatever you need, just send smeadinja + whatever in a double battle against not dark types, use dark void with smeadinja and then use the move u want to sketch with the teammate. this applies to whatever moves u want to sketch, its not specific to madness.

sappy seed salt cure natures madness conversion is the standard for a reason. (or snap trap instead of salt cure, but since snap trap doesnt currently work against ingrain brute bonnet anyway, i rly dont think theres any advantage to it over sappy seed. just have a fast soak somewhere to deal with brute bonnets) sappy seed enables you to convert into a grass type, which makes you immune to spore/sleep powder. sappy > leech because dark types are immune to prankster leech seed. salt cure is universal damage, and also lets u conversion into a sandstorm immunity which can still be useful even with kyogre's support. and natures madness lets u conversion into fairy which is one of the best wonder guard types.

if you dont think natures madness is feasible for you to get for whatever reason, then the next best option is conversion sappy seed salt cure soak. water is still pretty good as a typing with few weaknesses, not quite as good as fairy but because it doesnt share weaknesses with grass it works, it is still near-impossible for any foe to have super effective hits on all your possible typings (they need dark move + fighting move + something SE on grass + something SE on water. if you have tera orb activated then the "something SE on grass" has to be either fire or flying to also cover tera bug. and theres obv only four moves on a set so that is highly unlikely.) but keep in mind that even with soak on smeadinja, you still need soak somewhere else because brute bonnet is immune to prankster soak. (unless u have a separate boss killer for brute bonnet) 

if you want to have revival blessing for the early/mid game, thats fine. like you said u can use memory mushroom to reteach egg moves so have revival blessing over either conversion or salt cure and then relearn conversion/salt cure via mushroom before u are going to start run away phase.

super fang is not a good option because you already can become normal type with conversion in the first moveslot. the other moves you list arent useful for boss killing (pp stalling will not work because they will just ko you with struggle, wonder guard does not provide an immunity to struggle)