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I'm running Carrion Crown for a group of friends, and they're nearing the end. While gearing up at a wizard npc I made up, one player decided he didn't need anything else, and instead gave the wizard 30,000 gold and said "Make the biggest bomb you can." He then gave him his Ring of Retribution to be used as part of the bomb, preferably the trigger.
So now I ask you, experienced community, to help me satisfy my player. A few things to keep in mind.
The wizard doesn't strictly work alone. If a specific feat or class ability is needed, make up any npc you need to.
Forget how long it would normally take to make by RAW. They're nearing the end of the campaign, I'm letting them have at it.
They won't be carrying it themselves. The wizard will get it to them once they've decided where it'll go; the Witchgates won't be an issue.
Don't feel obligated to include the ring in the bomb. The player is pretty lenient, so he wouldn't be too upset if it wasn't.

If I reach a level where I gain multiple feats, such as one through level up and one as a bonus combat feat, can I take a pre-req feat and the feat it's the pre-req for at the same time?
For example, Improved Critical and Seize the Moment?

Rangers get a lot of good stuff that I feel can compliment a Magus pretty well. I play in non-optimized campaigns, so an idea like this might not be so bad in the long run, but I would still love some advice for making sure I can still stay relevant.

Magus - Spellstrike is the key ability in this build, making this the class I'm going to be favoring levels in.
Ranger - The good BaB progression and free feats are what interest me here, I can see myself taking up to 6 levels of this.

I'm an aspiring DM whose currently just running Adventure Paths until I get a better understanding of the game to homebrew my campaigns. One thing I've become concerned about is if player stats can reach a point of absurdity, that it becomes unbalanced in their favor. This hasn't happened to me yet, I'm just wondering if it's something I should look out for.
As a side question, what would you say is the highest reasonable number for a stat? I imagine this number would be different for each stat, right?