I use whole egg, because it is easier and I don't have a half an egg. I also use vinegar, unless I want lemon as a flavor. Vinegar just means less liquid for the same amount of acidity. You COULD use an emulsifier, such as powdered mustard, some type of gum. etc...but, that is adding stuff just for texture. If I want to add lemon, I will grate some zest and muddle that into the vinegar. It takes on the lemon aroma without adding water. Excess liquid will be your problem.
Commercial mayonnaise makers use things such as guar gum and xanthan gum to aid in keeping the texture dense and emulsified. They also use a commercial vinegar or commercial lemon extract, which is much more concentrated than household vinegar or real lemon juice.
I'm feeling bearish, and I'm packing a Wusthof Grand Brisket slicer from MABA
"perhaps...but then again...maybe not..."