We've had no problems building up to four pre-season
BunnyBots out of one lab with the same mentors advising all the teams. No two BunnyBots were even close to being the same. Where things may have gotten complicated in the 2898/1510 case is having students crossing over between the teams working on each others robots.
Building twins seems fine if that's what you decide to do but then it should be clear
up front that if neither team qualifies for Championships then the organization is sending 2898 (because 1510 couldn't get a lottery slot since they went last year) and that it will be an all-star drive team and pit crew made up of members of both 2898 & 1510.
Building twins does reduce the engineering being done which might be good if those resources are limited or less than optimal if there are students who aren't fully utilized. It is also somewhat cheaper since you only need one set of spares and one robot might be available as a practice robot if the other is on the way to champs.