Sure, a simple enriched bread like challah you can go by feel but you're going to have a lot more trouble succeeding with sourdough panettone without a tested recipe exactly because it is a living organism.

Of particular importance are the ratios of starter-flour-water when refreshing your culture (thrice daily! then bundling or floating for overnight storage...) It influences the ratio of Saccharomyces to Lactobacillus which has an effect on the pH of your dough after the first or second fermentation. If pH goes too low the gluten will dissolve and your dough will disintegrate when you try to knead in more ingredients.

One of the USA panettone masters, Roy Shvartzapel, insists you need a pH meter to be successful but after flailing around with one I found copying the refresh ratios of one of the Italian masters to do the trick. Unfortunately, refreshing is usually not part of published recipes!