| Trenas |
My recommendation:
I know this is not Paizo rules, but its a system that I have found works well and keeps Lycanthrope PC's from being too overpowered. It still gives them distinct bonuses and flavor from being a were-creature, but keeps them more a less in line with normal PC's (considering the +1 level requirement that Paizo set up for Lycanthropes).
What I would do in my game would be to apply stat mods (from the base creature) in hybrid form, and slightly boost the mods for physical stats in full animal form. For mental stats (Int in particular, since Wis and Cha are usually well represented in animals stats. They usually come pretty close to the human baseline anyway) I would apply a flat -2 Int modifier in Hybrid form, and a -4 Int mod in full animal form. The reasoning: Shifting causes the were's thought processes to become more bestial in order to properly function in animal form.
All Lycanthropes would receive a +2 bonus to one physical stat in all forms. IE: A were-fox would likely receive a +2 to Dex, while a were-bear would probably receive it to Con. A badger or wolverine would probably get a Str bonus. Basically, pick a physical attribute that fits the animal (Graceful animals get Dex, Strong animals get Str, Hardy animals get Con) and apply a permanent +2 Racial Bonus to characters relevant stat.
Physical stat mods would be based on the animals base stats. IE: A fox has a fairly normal strength stat, so it wouldn't give a were-fox any bonus to strength. He would instead gain a +2 Dex, +1 Con while in Hybrid form, and a +4 Bonus to Dex/+2 Bonus to Con while in full animal form.
Basically use the following guideline:
Base Animal Stat:/ Hybrid Mod:/ Animal form Mod:
3-5: / -2 / -4
6-8: / 0 / -2
9-11: / 0 / 0
12-14: / 0 / +2
15-20: / +2 / +4
21-25: / +4 / +6
26-30: / +6 / +8
I would also completely forbid Dire animal base forms as Lycanthropes, at least for PC's. Perhaps for some massive Were-lord type creature, but no way would I allow PC's to go there. Its simply too overpowered and clumsy in every rules system I have seen for Lycanthropes. As for game reasons: Such lycanthropes would be Primal Aspects, their were-nature based on some deep blessing or curse brought on for truly heinous/outstanding deeds.
The normal animals in the various bestiaries would (at the high end, using a Grizzly Bear as base) grant a character a constant +2 to Con or Str. Hybrid form would have a total: +4 Str, +2 Con, +1 Dex, -2 Int. Full Grizzly Form would grant: +6 Str, + 4 Con, +2 Dex, -4 Int.
Very powerful, but not so stupidly powerful as to completely wreck encounter levels.
This system also neatly addresses the whole "how do I apply the +2 modifier", and makes a characters base stats still relevant in all forms. A wizard with a strength of 6 shouldn't take a full round action and suddenly become a melee powerhouse with a strength of 18 or 20 and full ability to still use magic (Natural Spell feat if allowed by DM, or other custom/3rd party OGL feat). At most, that 6 strength wizard would be going into melee with a 16 Str. Useful, but not game breaking. This system also naturally takes level based stat increases into account without issue.