Be careful with that one, the answer is, it depends. The flight envelope of the ME 109 and a WWI plane are quite a bit different. The ME, with the retractable landing gear will limit the prop size. Since the WWI model will want to spin a larger prop, the requirements are somewhat at odds. Geared motors are no longer popular, so you will probably be using an outrunner type motor. To accomplish what you would like to do, you will have to use batteries of different voltages for each application. The ME will probably require a 5S (18.5 V nominal) battery while the WWI plane will probably use a 4S (14.8 V nominal) battery.

Personally, depending piloting skill level, I would pick an airplane that is easy to fly for a first conversion (ie. CUB or something of that sort) so that you can spend you time learning about electrics and getting a feel for it. Probably the first thing you will notice with electrics is that the lack of sound throws you off. It takes a while to learn to manage power based on thumb position while getting very little sound feed back. Something like the ME will be more critical of power settings (specially on landing) and make the transition more challenging. By the way, my first electric was a high wing plane followed by a sport/3d plane.

Good luck,

Teo