If you are determined to use Venusaur as a sweeper then you absolutely need a Talonflame check. Heatran is the first who comes to mind as it benefits from the sun but Rotom-W comes to mind as well as having two fire pokemon may feel redundant and Rotom-W can also offer much utility in volt switch and thunder wave. Just my two cents.Is building a team around CharzardY and venusaur in the current meta? Would slowbro be a solid trio for a fwg core?
Tentatively I'm kinda thinking of making my team with this general outline.
Special sweeper- CharY
physical sweeper- Dragonite
Sun team benefitter, mix between o and d- venusaur
Physical wall- slowbro
defog/stealth rocks/will o wisp- mew
Not sure who my last spot would go to, tentatively consisting clefable unless there is a better option or a pokemon I have to try and check.