TL

R.
IF cars couldn't run properly on 11-14v (which they can) FLA would be the better option.
IF you are not using the car as a weekly driven car, you would need to charge manually, FLA or LTO
IF you charged the LTO from flat to full, you may have an issue (which doesn't happen)
Given real-world scenarios, FLA is objectively worse than LTO, although some adjustment is required for LTO (such as running 5s and lowering charge voltage to 13.5)
I am all for constructive criticism, it makes me consider more variables than I may have originally. Yes, LTO is not great for 12v systems. The question then becomes "Is it really a 12v system?" If you look at car audio guys, they regularly run 15v and don't seem to have any issues. Considering the inherent voltage drop to the car systems, plus the built-in capacity to go higher than 12 v, LTO doesn't look so bad. The starter seems to be the most directly connected system, which is not really an issue. Other systems will have some inherent voltage drop as well, also a capacity to run at 14v (or so).
In regards to them not being ideal, you are absolutely correct! In regards to "will it work?" that seems fairly certain.
35Ah is consistent with most FLA batteries sold in Aus, taking into account the 50% margin you mention. Is this an issue for a rarely driven car? Absolutely!* Is it an issue with a daily driver? No. The same goes for charging an LTO battery from an alternator. Assuming you have a "dumb" alternator, then charging for an hour at 35 amps is probably not good for it (or charging at 70 amps for 30 minutes). Will that even happen? Probably not. Taking into account my use case as a daily driver, the only drains will be starting and parasitic drains (car alarm etc). Starting takes 2 seconds (at worst) at 300 amps. The sitting drain should be 0.05 amp. So to recharge the battery after sitting for 5 days, starting draw for 2 seconds, would take a total of 30 seconds or less. (cranking amps at 300 amps for 2 seconds, idle draw 0.05 amp for 24x5 hours, recharging from alt at 30 amps)
I am unsure how you mean the power system is designed for a different chemistry. I see this as an argument similar to "the existing charging is inefficient, so if you put it on yours, the inefficiencies will make it bad." However, if you work from first principles and ask "can the charging system work, even though it is made to work with poor batteries?" you have a different question.
Yes, FLA needs float etc, but this is not required for LTO. FLA has a charging efficiency of 75-80%, whereas LTO is close to 100%. This means an LTO system is inherently "better" for the charging system. It also means that the "reserves" of a FLA are only available if/when you inefficiently charge them for extended periods, thus putting more strain on the alternator. I can't say that FLA is better for the charging system, given these numbers, and the use case.
Given the use case, and the capacity of the car's electronics to work comfortably at 14.5v, I don't see FLA being better. Plus they cost more...
The server rack LiFePO4 batteries are amazing, best chemistry for solar setups.
*On further consideration... a FLA will self-discharge at about 4%/week. LTO will self-discharge negligibly in that time. A 300 Ah FLA will discharge about 12 amp in the first week, so at some point the LTO will be better, in regards to capacity remaining. The math is too hard for me to bother doing atm though

You would expect about 8Ah draw from sitting draws per week. An LTO would probably start a car after 2+ weeks, same as a FLA. Any more than that and I would expect you to charge/run either battery for s while. The FLA will take longer to recharge in this case.