Is there a way to join pacers without having to log off after a warm up
Unfortunately that is not a current option. At current the only way to ride with a pace partner is to select them from the game startup OR to catch them on the open road and self navigate to follow them.
I have had problems switching between the bots. Takes a while to log out and reenter but frequently upon re-entry, it does not put me in the peleton with the bot but instead I end up on my own
There is one, VERY cumbersome and inefficient method. Choose a pace 'bot from the drop in screen, but perform a U-turn immediately. Do your warm-up (the length of which will be determined NOT by you, but by other factors, as you will see…) The game will keep you on the same (reverse) route as the pace partner you originally chose. When you see the pace peloton approaching, perform another U-turn and join the 'bot. This requires skill and alertness! LOL. Obviously, the length of time that it takes before you re-encounter the 'bot will vary depending on WHICH partner you initially select and which route he/she is running. And, if you miss-time the crucial second U-turn, well, you’ll have to continue warming-up until you run headlong into the pacer 'bot again. Luck!
This function could very easily be achieved by allowing users to set a pedal assist time. It’s clearly not an issue to have a period where pedalling is easier, if the user could alter this in settings it would at least give them the opportunity to get 10 minutes warming up in without too much guff.