Pure external when tibia is as straight as an arrow

Is it safe to do pure external with circular Ilizarov frames when tibia is perfectly straight? I don't want to get misaligned tibia after the distraction but also want to avoid LON / LATN.

To my knowledge, circular has a lot less risk for misalignment because you can manipulate the bone in multi dimensions, unlike lateral externals. I'm not sure how much the presence of an internal nail (lon) is crucial in causing misalignment and anyway with circular ring you can control it during lengthening.
Keep in mind that with external only it will take a long time for you to be able to bear weight because you don't have the internal nail support, and with tibia bone healing takes at least twice the time of femurs..

I know that circular frames is best for bone manipulation but I'm worried about the consolidation phase since I won't be having IM nails inside the bones and might get misalignments during weight bearing on the frames. Is there a way to avoid this besides not bearing too much body weight on the frames?

If you do pure external youll be able to remove the frame when your bone healing is as closest to complete, surgeons would prefer the maximum consolidation before they remove the frame because they wouldn't want to risk any bone fracture or misalignment, while patient suffering enduring the frame is second in importance....
The amount of bone healing when you remove the frame will determine how much weight (if any) you can put on the leg.
The anterior and medial aspects in tibia are the last to heal, so bearing weight too early may cause a varus deformity.
I would say go for lon /latn rather than pure external for minimizing the amount of time with the frame which can be hell. Although there are risks of nail /bone infection...
If you have time to spare and a lot of mental strength and patience maybe externals only is the safest...

So, if I do pure external and when they remove the frames, I won't be allowed to weight bear for some time and shall use crutches? How long should I wait post frame removal in order to start driving a bike for example? Or walk unassisted.

As I said, your walking after removal depends on your bone consolidation status at time of removal.
If you wait until full consolidation you may walk pretty much after the removal surgery, minus maybe a a week or two with crutches or some sort of a support (like a t-scope) just for safety.
Otherwise, it depends on your bone healing,. You'll need regular x-rays to monitor the bone consolidation before you're ok to walk unassisted

I won't remove the fixators until the bones fully heal in order to prevent bending and height loss.

Yeah, being in frames for about a year is not easy, but at least I can get 5.5-6.5 cm of height in that period of time which is game changing jump from my starting height.