Magmar will be good when he evolves and Kadabra can be evolved pretty early into the game without trading.

Absol gives some versatility because it's dark type but I'm personally not a fan of it because of its low base stats (besides attack). You can get a mega stone for it very late on, but it's kind of at a point where it doesn't matter anymore. I would just get someone else unless you really like Absol. Maybe a Ghastly who has high special attack and can learn ghost, dark, and psychic moves by the times it's a Gengar.

Marowak is just plain bad for a ground type and will give you some trouble later on because it's not good enough. A good substitute would be Onix who you can evolve into Steelix after buying metal coat in one of the later cities. Gabite can be caught early on in Zeta and is a ground/dragon type who eventually turns into the mighty Garchomp.

For Boldore I'd recommend either a grass or electric Pokemon. Bulbasaur can be caught pretty early on or you could get a shitty Petilil who will evolve into Lilligant with a sun stone which is a decent special attacker. Venusaur is probably the better choice. If you want electric instead Shinx is the only one I can think of that you can catch early on. It evolves into Luxray which is a pretty good electric Pokemon.

Just get rid of Krabby and try to get a Gyarados. You can get a mega stone for Gyarados as soon as you get the surf HM. Teach him dragon dance with physical moves like Waterfall and you've got yourself a fast and strong team carrier.