in all honesty I have 3 different ways to buff sceptile. A. give it more variety in it movepool(specifically special attacks). B. switch ATK with SpATK like you said while also changing its ability to benefit its swapped ATK stat(tough claws, sharpness, sheer force, etc.) its fast enough as it is so it doesn't need to be faster. and of course C. which is just swapping ATK with SpATK stat like you said.
Something that needs to be mentioned tho, stat spreads for VGC are usually worked around the current meta. If you want to have an offensive mon like Blaziken, you usually don't always want or need it to have 252 attack and speed, as Speed boost usually gives him an advantage over most mons even if at 140 EVs, also on the offensive side, look out which Pokémon he got favorable matchups, and try to get a good dmg balance. As this is lvl 50, most of the times you wont be OHKO mons unless they are 4x weak, or seriously frail.
