You need to stop making a new thread every time a non-specific thought pops into your head.
No. You build your team based on synergy between each member. The idea that one singular Pokemon can allow you to throw almost anything into the other five slots is quite frankly laughable in competitive circles. You craft a team with each member fulfilling a certain role, covering a certain weakness, etc. There's nothing stopping you from choosing what you want but if they're not picked with a specific niche/role/etc in mind then it's probably not gonna go far. Even the infamous Pachirisu example was chosen because of the role it filled.