Rule V §32 Use of Type-Form Indicators with Letters ... (The italic indicator is listed as dots 46) The appropriate type-form indicator must be used to express the type form of a letter. The type-form indicator for a letter must always be followed by an alphabetic indicator (for English, it's dots 56). So, by inserting the letter indicator following dots 46, you are saying that dots 46 is an italic indicator.
The multipurpose indicator must be used after the decimal point symbol to indicate that the symbol which follows it is not numeric. Rule XXIII §v. In this situation, the dot 5 is a multipurpose indicator not a baseline indicator.
I can see where the reader might confuse the meaning of these symbols, but context and discussion would define the use of the decimal point.
I don't know what kind of advice I should give you about switching to a different "system". Perhaps that should come from the requestor of the material. If the book is to be registered for others to use, a correction should be made to assure that this is treated identically in all volumes of the book.