Some faithful remake of concrete ST model is in plan. Look for it in this forum - exxosuk is who started thread, where you can even suggest some features.
Idea is to make same core, with original CPU. Some components may be not original, but remakes because of sourcing problems. Some expansion connector changes are planned, for instance.
To add that Atari ST remake is at least 10x harder than Spectrum remake, even if it has no 10x more components.
Considering FPGA clones - that's most popular way now, as I see. Price is good, it is not for only 1 computer model. + you don't need to hunt old peripherals like monitor, keyboard etc.
Of course, there is incompatibility with some SW, games, more than with original. Hmmm... what I talking here Yes, there is no 100% SW compatible ST model. TOS version and even RAM size in machine may cause some SW not working. But here must to add that in most cases the real cause is poor coding of such SW, and it can be solved to run. But then, it can be patched for FPGA too.
What is most original requiring are fancy demos using plenty of undocumented, specific HW features (I would call it rather side features). Then you have practically 3 choices:
1 get original, including old monitor or TV.
2 Use emulator on some PC ...
3 wait for some faithful clone. Now. the last option is a lottery in fact in some way. Somehow I don't expect that we will see 100% faithful clone ever. Unless some billioner (for instance Georg Soros suddenly decides to do something useful and good in his miserable life) will pump some serious money in it, what will never return .
For some medium retro activity - like gaming, little coding, 100% faithful is not necessary. I talked years ago about that we will have gradually less and less working oldies, and that fixing them will be problem and costy. 30 years old electronic is such. I see around plenty of old TVs ditched. Some are even in working condition. But they are not rarity, and are not 30 year old.