Hybrids (or in our case, tribrids heh) are alluring for many reasons, wanting the "best of both worlds" an almost irresistible goal, the range of an ICE combined with the quiet efficiency of an electric drive is definitely something to look into... but hybrids are an extremely tricky balancing act between efficiency, weight, drag & ofc complexity. While there is lots of potential, there is also the hazard of diminishing returns and the added complexity can become a bit "Rube Goldberg" in it's own way...
Just as a hypothetical example, the genset trailer powering an electric bike concept. While it has been done a few times, a good question to ask would be - which would get better overall fuel mileage, an ebike complete with batteries towing a generator & all it's integral components - or just the engine from that generator (or it's equivalent) powering the bike by itself, without all the added weight & drag of the trailer, genhead, batteries & electric motor?
To compound the difficulties, expense - will the additional costs of two different motors, generator head & batteries make up for itself in reduced fuel consumption, if there is an appreciable reduction? If so, how much and how long will it take before it pays for itself? After all hybrids, even straight electrics don't eliminate consumption, they just defer it & unless there's another source of power from solar or wind to use as a charging station (and those cost too) - there's many questions raised about the fuel used & it's resultant costs for even electric vehicles... there's the sustainability aspect, but unless the genset is alcohol, hydrogen or diesel powered - that's a moot point with a hybrid.
Don't get me wrong, I'm not trying to dissuade experimentation by any means - after all I'm building a hybrid/tribrid myself. I just think it's important to recognize the intrinsic difficulties and how they may effect your goals, and what those goals may be. Electric vehicles have been around since the late 1800's & hybrids have been in use since the late 1930's - yet even modern, commercially available hybrids are still quite controversial, the overall efficiency & impact of the Toyota Prius a prime example.
I would have to say if your primary interests are simplicity, range & power as inferred by your post, then either just a small & efficient four stroke engine or a straight ebike with the best batteries you can afford are the most cost effective options... but if tinkering and the joy of experimentation are of more interest to you than even end results, then by all means go for it & please, keep us apprised of your progress
