We’ve used the model Crowdcube structure in previous rounds, where investors have either A or B shares. Both classes of shares are the same except B shares do not have voting or pre-emption rights. You get A shares by investing more (different threshold depending on the round).
In this round, pre-emption rights are irrelevant as all existing investors have the opportunity to invest pro-rata, or more or less if they want.
In the future, we plan to still give all existing shareholders a chance to participate in future funding rounds. You could compare this to Monzo, who only offered B shares (ie no pre-emption rights), but still offered the small crowdfunding investors like me a chance to participate in their last round along with institutional investors.