Don’t let those pissy comments spoil your day! Their bad moods are their problem, not yours!
Most of the belt drive tables you mention are made by Micro and have much in common. The Luxman PD-310 and PD-350 are close relatives to Micro BL-99V. I owned the PD-310 which sounded very nice, but I simply didn’t like the operation of the vacuum hold down. I replaced it with the BL-91G with gunmetal plateau, which is significantly better than the PD-310 (with aluminum plateau). The PD-350 has very heavy plateau and chassis and will likely be superior to BL-91G and more similar to BL-111 or something. If you like the vacuum hold down that’s the one I’d keep.
Selling some of your tables would provide funds to get a better arm for the PD-350. Plenty of choice, but I’d guess an FR-64S or FR-64fx would be a great choice for your Allaerts. The only problem will be finding the correct arm board. The ones used on the Luxman are different in size from the Micro A-1200/1500 series and are very hard to find, especially the preferred gunmetal version (standard version is aluminum).
I wouldn’t waste my time on ’modern’ equivalents, they’re not likely to improve on the PD-350. Unless you’re willing to pay funny money.......