Unfortunately, the liveries feature in Experimental requires additional characters to be inserted into the definitions of a vehicle's images as in the following example:
EmptyImage[E][1]=./images/lnwr-bloomer-tender-black_E.0
The version without the livery definition is:
EmptyImage[E]=./images/lnwr-bloomer-tender-black_E.0
This means that it is no longer possible to use .dat files written for Experimental and that use the liveries feature with the Standard makeobj (and there isn't an easy way around this, as the liveries code re-uses large parts of the freight images code). This is most unfortunate for any dual pakset such as Pak128.Britain. Would it be possible for the Standard Makeobj to ignore the Experimental livery definitions such that the .dat files once again work equally in Standard and Experimental?
Yes, it would be possible. There is only one person needed who does it. My first choice would be the guy, who implemented the livery stuff for experimental and thus broke the things you mentioned.