Additional question: what if you have multiple PCs with multiple ranks in this talent, such that they would all be drawing more cards than the 10 available? Example: 3 players with a PC at Rank 3 in Lightning Fast would need to draw 12 cards. If they all draw "at the same time" this corner case is impossible to satisfy with the 10 card initiative deck.
Really this is a question about rule intent in regards to initiative card draw order: was it intended that a player whose PC has this talent actually draw before any other player (with an expectation that in most groups only 1 or 2 players would actually select this talent), or is the "and shuffle the other one back into the deck before others draw their cards" verbiage simply meant to convey that regardless of the player draw order (which is not specified in the rules explicitly) any player with this talent simply needs to return their cards to the draw deck before another player would draw one or more initiative card(s)?
You may be over thinking this as the scenario above is quite unlikely but can be handled with some common sense.
If it were me I would maybe get each player to draw a single card, this would then dictate what order they activate their talent in, immediately shuffle all cards back in the deck.
The first person would draw three cards, keeping one and shuffle back in the discarded cards, then the next person and so on before anyone without the talent draws a card.
If there are multiple characters with different ranks in this talent I would allow rank 3 to draw first, then rank 2 etc.