My favorite "if so-and-so..." in baseball history is Ted Williams' career with no war interruptions.
He actually hit .344 with 2654 hits, 521 HR, 1839 RBI
He's 75th all-time in hits, 20th in HR, and 14th in RBI.
With average (for him) seasons instead of going to war:
.342 with 3452 hits, 663 HR, 2380 RBI.
.
So in hits he'd move up from 75th to 7th.
In HR, up from 20th to 5th.
And in RBI, from 14th to 1st.
And those would be his rankings NOW, not when he retired.
At his time of retirement, had he not served:
3rd all-time in hits
2nd in HR
1st in RBI
.
He'd actually have been in Babe Ruth territory, and with more volume.