Yeah think limiting it to 1 per server seems fine, especially if they made it so every character you had for that server had full rights to it. I noticed after the influx of refugees into Mateus a few people took advantage of the gil they could bring over and bought out several plots, a couple of them nearly buying up a whole ward's worth so yeah... doesnt seem right when new and returning people/free companies want them as well. Only other solutions can really see is adding a small yard/balcony to apartments so you have something closer to a small house, limited something like 1/2 of houses to only free companies of which they may only have 1, or just simply adding rent to plots 100k-200k a week or so, to make holding those vast amount of plots extremely difficult.