@KK, this is a good point. I honestly thought that 4GB of LONGTEXT was reached before I saw real editables definition.
Anyway, managing of 200+ rows is a pain for the enduser, so upping the php limit would be worse than putting each repeatable in a separate group (to make them collapsed), order groups from recent to oldest and, in its best, convert the whole shebang to cloned pages
@cjcort cloned pages would allow your client to 'unpublish' a marker without deleting it from database, quickly find a marker by its name, make any kind of selection or report (e.g. 'Show all projects by a certain architect' or 'Show projects on map by a chosen city '). Then with the infobox on map it would be possible to add images, extra info like address or phone number.
It will be manageable and pleasant to work with. More features (sorting, ordering, custom map markers, filters) may bring you more money for this job.