- Only if it was designed poorly, with insufficient material wall thickness and welds. Pure material comparisons are largely irrelevant until you look at exactly how much and how they use it.
- Proper use of grease on the pedal spindle threads largely resolves this. For an indoor application that I expect get more sweat than outside, I would personally use a heavier grease (moly axle specifically) and LOTS of it.
- This needs similar attention regardless of material. If left with no lube, aluminum to aluminum contact can gall over time and lead to super nasty freezing between the parts. The remedy is to use appropriate grease that serves as an insulator, just like a typical application for an outside bike.
Most of the issues you mention are worth consideration regardless of, and are not solved with a change of material. They are initial assembly and long term use / care issues required for any bike used in this case (that includes regular bikes on trainers as well as dedicated indoor bikes of any kind). “Set it and forget it” approaches that we see to often will lead to issues for any of these bikes and materials.
- Correct, proper design and manufacturing, coupled with appropriate care and maintenance effectively eliminate all those concerns above.