I am someone who enjoys the achievement aspects of games and find this to be highly addictive, while also giving direction/activities to do.

What do people feel about having some achievements for specific key groups of smaller achievements? Kind of rewarding people who invest time into trying to finish/focus on completing alot of these?

For Example:

Drug Specialist Achievement (Complete all Tier 1 Drug achievements)

Jail Break King (Complete Tiers 1-3 of Jail breaking)

True Mobster Achievement (Complete all Felony achievements)

Gun God Achievement (Complete all Killing achievements)

Some of these achievements are quite hard and need alot of time to complete so having the above bonuses would be a little extra completion incentive and offer a nice reward.

Can't say I'm a huge fan of this. If extra money/xp were to be given for achievements, it would have to be countered by lowering the amount of money/XP we get from the actions themselves. 

Why do you say that? I dont think the two relate at all to be honest.

For example,

Marijuana Mover - Full Load Sold At A Profit 5x

 This pays out money/xp for the achievement but has no relation to the action itself.

My suggestion was only for like 3-4 new achievements, kind of like "Platinum/Legendary" type of achievements. The payout could be anything ranging from $500k even. It's more just aimed at an additional reward for completing set groups of achievements to the full.

Do any achievements currently directly relate to the actions?

I think perhaps I'm misunderstanding your question. Does the Rogue achievement directly relate to shooting Rogues? Yes. Do the OC achievements directly relate to running OC's? Yes. Does the KO the PO achievement directly relate to Knocking Over the Post Office petty? Yes. 

Maybe I'm just confused :x 

Ok you are confusing me too now xD

Here is a different example of what I mean.

All the below achievements already exist and have their payouts:

 

Goomba Gunman - Kill 5 Goombas

Earner Ender - Kill 5 Earners

Wise Guy Wrangler - Kill 5 Wise Guys

Made Man Murderer - Kill 5 Made Men

Capo Capper - Kill 5 Capos

Boss Bomber  - Kill 5 Bosses

Consigliere Cutthroat - Kill 5 Consiglieres

Don Damager - Kill 5 Dons

Godfather Galvanizer -Kill A Godfather

 

My suggestion is, an achievement like this:

Gun God Achievement (Complete all Goomba to Don Killing achievements)

The money/xp rewards could be anything, it's more about the challenge of completing all the achievements in the group. It would have no relation to money/xp but if that was still an issue, then perhaps the payout on the achievements within that group could be lowered to make the final one a worth value.