I have a suggestion
Do a pole like you have done for so many things previously
Ask folks who would like to delay their shipment in favor of having onboard LTE and who would rather have early.
If you could give a timeframe on how long it would take to get LTE with the understanding that certifications could have a significant impact to the quoted timeline, if folks with preorders would like to delay by 2 - 2 months (I am putting words in your mouth, I apologize) but get delivery of an LTE model, then there may be an opportunity to have a version 3 shipment which includes LTE, without derailing Feb/Mar and the second batch. There would of course be preorders that would wait for a shipment a little longer, but with the length of time folks are waiting, they may find this acceptable rather than cancelling their order.
I don't know if I am opening a can of worms, and if I am, I apologize. It may also require rejiggling the order status based on who would rather wait. I suspect an LTE modem would add approximately $100 to the unit, again I don't know if I am speaking out of turn, the real issue is the extra certifications for LTE and the placement of a SIM card,
As for me, in the states, I would rather tether to the EVE V than give the carrier another $10 per month to avoid tethering. There is no real need for me to have an internal LTE modem, I have a Wifi in many hotspots plus I have a SIM in my car which I can use as a hotspot in emergencies, plus can tether to my phone if needed. But I understand that many folks saw LTE as a requirement or a very much appreciated attribute, so the survey is suggested.
And of course, prepayments are prepayments, I would not suggest you return some funds to only collect in a couple of months, that would be truly silly.