How about you sort the column that is being the source for the drop down / Auto complete? Once you set a sort on the column in the report definition rule, the data that form the source for these DD / Auto complete, will get sorted automatically as they are getting displayed.
The behaviour which you are describing is the normal sort for a text field.
When sorting text, implied blank padding sorts ahead of any other character, so "V.31" will sort ahead of "V.31.x".
Also, since the value is text, numbers in the string are also considered as text, so "V31.45" sorts ahead of "V31.5" (because "4" sorts ahead of "5").
You are expecting that the numeric values be sorted in ascending numeric value, such that 5 sorts ahead of 45.
What you are describing is the need for a custom sort to sort the values for this property partially as text and partially numerically.
You need to create a custom sort which will break the value of the property into its respective parts and sort each of the parts working right to left (minor to major sort), appropriately as text or numbers, to arrive at the sort order which you are describing.
Once your custom sort is created and defined in a library that you have added to your ruleset, you then need to use the Override Sort Function field on the property's Advanced tab to specify the name of your custom sort.