yes, you can make your syther stronger.
but, its still a bug pokemon.
bug is weak to flying.
everyone has pidgey, pidgeyotto and pidgeyot.
I have a 1823 pincir.
when I put it in a gym, its so that we can level the gym quickly wiht pidgeyot and gain 1000 prestiege when beating it with a 900 CP flyer.
now add in that bug is also weak to fire and rock and suddenly the options to beat the syther just triple.
while I am not saying you should not be using the buddy system to make it stronger, what I am saying is that walking with a magicarp to get a gyrados might be a better use of your time.
I plan on leveling my dratini, my magicarp, my snorlax, getting the last few candies I need for my koffin, grimer, kabuto, omnimite, pikachu, squirtle and charmander.