Would you rather fly an aircraft with 100 hp and a MTOW of 490 kg, or one with 740 kg, if the useful loads were identical? The improvement in power to weight gives very impressive performance, including 1600 fpm and stol. A 750 kg aircraft would be underpowered and not so much fun. The Micros often have a higher empty weight due to the reduced stall speed requiring more wing area and bigger flaps.
Alternative engines are the Jab 2200 4cyl(85hp) and 3300 6cyl(120hp). Simple, modern air cooled, but not considered as reliable as the Rotax.
If the aircraft is a factory built VLA than no problem with instruction for a group owned aircraft. If home built you cannot be instructed for the issue of a licence, but you can do BAFR, type conversion etc.
VLA is VFR only, but if you get an IMCR then no problem practicing you skill under the hood. If you have the skill and the kit it could save you life, so why not.
If you are concerned about UV, you could buy a full set of covers for the aircraft. Having owned several metal aircraft which were kept outside I would not recommend this for any aircraft, but sometimes there is no option. Have you considered trying to find a strip with a hangar? The above aircraft would be fine for this provided it did not get to muddy in winter.
Sywell have the metal AT2 VLA for training. Why not pitch up and have an hour in one?
Rod1