Conscription, as you suggest, does indeed provide military skills for all. But, unless you have programme of retraining to maintain these skills, the initial advantage is quickly lost. Nations that have a volunteer military usually have a well-developed reserve system as well. If you don't like the full-time military, you can serve 'part-time' in the reserves. And it is not, as you suggest, nations that are wealthy or that have high populations that can afford to scrap conscription. New Zealand, for example, (Guess where I'm from...) has neither a large population & certainly wouldn't deserve to be classified as 'wealthy', has an all-volunteer military. NZ's armed forces also have a very high level of respect for their professionalism. Even the US, after their experience in Vietnam, abandoned conscription. Volunteers usually ahve a much higher esprit de corps that their conscripted bretheren.
One fundamental difference between Taiwan & both Israel & S. Koera is that, unlike Taiwan, Isreal & S. Korea have extensive land borders with their potential adveraries. All manner of sneaky goings-on happen all along land borders... sometimes even fully-blown wars... Isreal also has a large part of it's armed forces on 'occupation duty' (Other people's words, not necessarily in accordance with my own views...) in areas immediately adjacent to it. Taiwan's security situation is nothing like that of Isreal or S.korea.
You also say that the ROC is in constant danger of being involved in a war. Do not forget that for much of it's existance, the ROC had, as a fundamental part of it's constitution, a section all about returning to 'The Mainland', beating up the communists & setting up shop in Nanjing. Perhaps the war the ROC is worried about exists only in it's own mind... And when the US had troops & other bits & pieces stationed here in Taiwan, the Chinese were more than a little worried of a US-supported, Taiwanese invasion of their country. (I read somewhere that China managed to soot down five ROC-manned U-2 spyplanes in the 1960's & '70's.)
But anyway, kunmingren, methinks we agree to differ on this.
cheers!!!