Is this your set?
http://mypdfmanuals.com/user-manual,SON ... 570163.pdf (Service manual link, unfortunately not the full document, but shows a picture of the set and the chassis identifier.)
I'm speaking from the US perspective, but I think I should have some basic pointers to get you looking in the right direction.
First, the safety of consumer sets for tate viewing - even before looking at the specific monitor, I would say this is bad. As you point out, these monitors are only meant to look good in normal portrait orientation. Somebody else might be able to give you direct input on that model (seems unlikely), but there are a few potential failings: the set might only be designed to take rough treatment when being initially shipped and installed; putting it into tate might put stress on parts that were never meant to be stressed, and the overall cabinet shape seems unsuitable; there might not be adequate vents or airflow design to allow warm air to rise through the system when put on its side.
Secondly, the utility of this model. I was looking recently at a US-area KV-27V45, which is apparently a newer model, but similar in some ways. It looks like a nice set, but the back panel only seems to have S-Video and composite inputs. For a serious gaming TV you want at least component YPbPr inputs - ideally SCART for RGB sources. There's no reason to accept anything less when there are people throwing out very nice CRT sets, or looking to give them a good home, right this instant. You can choose whatever size or make you want. Look for something new, and look in all your local online classifieds.
Finally, the availability of reasonably affordable pro monitors which are superior in
every regard save viewing size and possibly price (but think of it as a potential long-term investment). Pro monitors were, to the best of my knowledge, all designed with maximum flexibility and a relatively high degree of ruggedness in mind. I don't think that any cube monitors were designed by Sony with the understanding that they would be used on their sides, but they were probably designed with the understanding that they might be hauled off to strange corners of the Earth in support of A/V productions, and would be facing harsher stresses than just initial shipment and installation. A 20" PVM should weigh about 70 pounds, a BVM about 80 (sorry, I don't remember the proper mass offhand, and only remember the US weight numbers). Additionally, these monitors are flexible and many support all kinds of inputs - both Japanese and US region-compatible NTSC signals as well as PAL (some even autodetect this), RGB inputs suitable for playing many original arcade boards for the best vertical gaming experience outside of a dedicated arcade cabinet, component, and sometimes progressive signals for 480p / 576p consoles. Having this in a nice cube chassis with lots of ventilation points, handles on the sides, and an easy-to-manage cube shape means that you get a large number of positive design characteristics right off the bat. The only problem is sourcing one - they can be a bit expensive to find, and often need to be shipped from afar, and some shady sellers are trying to offload ones that are not in perfect working condition. That being said, these monitors often have tens of thousands of hours and the only issue is that they are a bit cheaper for their age. Lots of good choices here really.
Settle for the best, and good luck on your tate monitor quest!
I mostly got it for TV and movies so the only game systems it will see would be a PS3 (can I do audio over HDMI?) and also the NES (what kind of lag should I expect from SD input?) just because it's fun to keep in the living room. The weight isn't so bad, still a 2 person job but the shape of the casing is more of an impediment to lifting and moving it.
