I don't think the issue here is the size of the carrier - the QEs are pretty big after all - but whether it has cats and traps. On that, the UK has (as I think has already been noted) put out a request for information on acquiring a cat and trap system ideally capable of launching up to 55K lb and recovering 44Klb - recognising that in future a mix of manned and unmanned systems will become increasingly the way to go.
By comparison, the figures I've seen for MQ-25 suggest a MTOW of around 45K lb. Of course a healthy does of PPRuNe-style cynicism may be justified here given past experience in this area, but at least for now we seem to be planning for unmanned options including those that require catapult launch.
In the meantime, worth remembering that any operation against peer or near-peer opposition will always be carried out as part of a coalition effort. That's how it is these days and also how it will remain, and any discussion of QE carrier capabilities should recognise that. The UK, quite rightly, is not trying to emulate what the US could do on its own, or anything close.