D&D 3E/3.5 Mixing 3.5E and d20M power levels

[Halivar]

We're about to start a new campaign using a mix of traditional 3.5E and d20 Modern. Basically, the party's characters start as city-slickers thrust into a world of high fantasy. This will be our first usage of d20 Modern, and after looking over the rules, I'm a bit worried about the class power levels compared to traditional D&D classes (as the NPC's we'll meet will be).

Areas of my concern:
1) Fighters in 3.5E get +1 BAB/level, whereas almost all "fighter" classes in d20M get +2/3 BAB/level. Advantage: 3.5E fighter.
2) Fighters in 3.5E get all weapon and armor proficiencies, whereas all "fighter" classes in d20M still have to buy them with feats. Advantage: 3.5E fighter.
3) Mages in 3.5E get up to 9th level spells, d20M mages only get 5th level. Advantage: 3.5E mage.

Potential offsets:
1) d20M characters have class armor bonuses.
2) d20M characters get guns (but no STR mod, advantage is still to 3.5E fighter).

Does anyone have any ideas of how a d20M character can say alive in 3.5E land? Or is the original premise untenable? Can anyone else think of situations that would have to be planned for?

PS: I couldn't decide whether to put it in House Rules or d20 Modern, but I figured I may be looking at the mechanics wrong, so I put it here.

 

[silentspace]

You'd have to do a lot of work to do this. I noticed the other day that d20M Power Attack is 3.0 power attack.

Areas of concern:
1 - I don't think this is an issue. Strong seems to be the only "fighter" class in d20M, to me. You can still play a dextrous Strong Hero for the BAB.
2 - Weapon proficiencies don't seem like a big deal to me. Simple = Simple, Archaic = Martial, everything else is Exotic, just like in d&d
3 - d20M characters have no multiclassing penalties, let them multiclass into wizard or whatever they want.

Potential offsets:
1 - I would use the Defense Bonus alternate from Unearthed Arcana
2 - Doesn't seem like a big deal. D&D 3.5's power attack gives 2x damage. It's better than d&d missile weapons too. Plus d20M weapons do more base damage. Plus if you let them be enchanted they can do extra damage.

 

[Viktyr Gehrig]

If you're open to Gestalt rules, you could have your characters pick a D&D class and a d20 Modern class at each level. Fighter types can still have their +1 BAB, casters can get their full caster level, and the characters still benefit from Modern's richer mechanical depth.