The BAB system by raw has specific issue with it in that the Fighter seems to be rewarded least in a place he should be the master of. Especially since he shares the (full bab) with other fighter 'subtypes?' (the ranger, the paladin, the cavalier).  Other largely martial characters are also limited by the lack of variable attack bonus when placed in the midrange alchemists, and bards, and rogues.

What I've done is create a number of steps to allow variance... This alteration also makes multiclassing more complex than before.
Simple 'dipping' is nowhere NEAR a 'simple' as it once was...

0.18
FIGHTER WARRIOR HYBRID SEMI ADEPT MAGE
BAB 1.05   1   0.85   0.7   0.55   0.55
ITR CAP: < 7   CAP: < 5   CAP: < 5   CAP: < 4   CAP: < 3   CAP: < 3
1 +1 +1   +1   +0   +0   +0
2 +2 +2   +1   +1   +1   +1
3 +3 +3   +2   +2   +1   +1
4 +4 +4   +3   +2   +2   +2
5 +5/ +1 +5   +4   +3   +2   +2
6 +6/ +2 +6/ +1 +5   +4   +3   +3
7 +7/ +3 +7/ +2 +6/ +1 +5   +4   +4
8 +8/ +4 +8/ +3 +6/ +1 +5   +4   +4
9 +9/ +5/ +1 +9/ +4 +7/ +2 +6/ +1 +5   +5
10 +10/ +6/ +2 +10/ +5 +8/ +3 +7/ +2 +5   +5
11 +11/ +7/ +3 +11/ +6/ +1 +9/ +4 +7/ +2 +6/ +1 +6
12 +12/ +8/ +4 +12/ +7/ +2 +10/ +5 +8/ +3 +6/ +1 +6
13 +13/ +9/ +5/ +1 +13/ +8/ +3 +11/ +6/ +1 +9/ +4 +7/ +2 +7/ +1
14 +14/ +10/ +6/ +2 +14/ +9/ +4 +12/ +7/ +2 +9/ +4 +7/ +2 +7/ +1
15 +15/ +11/ +7/ +3 +15/ +10/ +5 +12/ +7/ +2 +10/ +5 +8/ +3 +8/ +2
16 +16/ +12/ +8/ +4 +16/ +11/ +6/ +1 +13/ +8/ +3 +11/ +6/ +1 +8/ +3 +8/ +2
17 +18/ +14/ +10/ +6/ +2 +17/ +12/ +7/ +2 +14/ +9/ +4 +12/ +7/ +2 +9/ +4 +9/ +3
18 +19/ +15/ +11/ +7/ +3 +18/ +13/ +8/ +3 +15/ +10/ +5 +12/ +7/ +2 +10/ +5 +10/ +4
19 +20/ +16/ +12/ +8/ +4 +19/ +14/ +9/ +4 +16/ +11/ +6/ +1 +13/ +8/ +3 +10/ +5 +10/ +4
20 +21/ +17/ +13/ +9/ +5/ +1 +20/ +15/ +10/ +5 +17/ +12/ +7/ +2 +14/ +9/ +4 +11/ +6/ +1 +11/ +5
21 +22/ +18/ +14/ +10/ +6/ +2 +21/ +16/ +11/ +6/ +1 +18/ +13/ +8/ +3 +14/ +9/ +4 +11/ +6/ +1 +11/ +5
22 +23/ +19/ +15/ +11/ +7/ +3 +22/ +17/ +12/ +7/ +2 +18/ +13/ +8/ +3 +15/ +10/ +5 +12/ +7/ +2 +12/ +6
23 +24/ +20/ +16/ +12/ +8/ +4 +23/ +18/ +13/ +8/ +3 +19/ +14/ +9/ +4 +16/ +11/ +6/ +1 +12/ +7/ +2 +12/ +6
24 +25/ +21/ +17/ +13/ +9/ +5/ +1 +24/ +19/ +14/ +9/ +4 +20/ +15/ +10/ +5 +16/ +11/ +6/ +1 +13/ +8/ +3 +13/ +7/ +1
25 +26/ +22/ +18/ +14/ +10/ +6/ +2 +25/ +20/ +15/ +10/ +5 +21/ +16/ +11/ +6 /+1 +17/ +12/ +7/ +2 +13/ +8/ +3 +13/ +7/ +1