Toilets that are fully enclosed (whatever they are designated) are less safe.
Rescue times are greatly increased if you can’t see who is in them and needing assistance.
In the Equality Act (2010), people with a disability should be able to have reasonable adjustment. So for people with epilepsy, diabetes, heart conditions, etc which causes them to collapse there should be safe toilets available. Obviously people (whether they have a diagnosed condition or not) go to the toilet when they feel ill so it is a common place people are found who have had strokes and heart attacks. Gaps safe lives.
Fire evacuation times are increased as well when you can’t see if a row of toilets is occupied quickly. Ventilation goes down and the concentration of disease borne particles in the cubicle air goes up. Hygiene is compromised further as mopping then draining urine/vomit/faeces/blood can’t be done as effectively.
The Government’s Document T (2024) for public toilets in shops, venues and offices is the relevant document. However it is for new buildings and retrofits. Unisex toilets are stipulated as fully enclosed and have to be easily opened from the outside and so the door can be made to open outwards. This is precisely because bodies block the door opening. The side effect of this of course is that you are in a private witness-free space and someone can let themselves in. Public toilets when they are privately enclosed have been called rape cubicles for a reason.
I analysed the research into Document T and it was flawed. There has been no impact assessment as far as I can see and certainly none published, on the consequences of removing these safety gaps for anyone having a medical emergency and for VAWG. There is plenty of evidence of incidents happening in enclosed toilets, particularly mixed sex, which includes historical data on disabled toilets as until recently they were the only ones without gaps.
In document T single sex toilet cubicles don’t have a specification on door height so it is up to the employer. Single sex designs can follow ‘universal’ designs (unisex) which are fully enclosed but unisex ones, like you state, should include a sink in the cubicle. If there is enough space for multiple toilets, it is clear in Document T that single sex toilets should be provided, then unisex. Unisex only are for when there is not enough room like in a small cafe.
Shockingly in the last few years the DfE have changed the designs for all secondary school toilets cubicles to have full height doors and partitions. When I questioned them about how this is safe for any pupils having a medical emergency (particularly as this is a common age to have a first seizure and for heart conditions) they said the school and governors should know their cohort (premonitions?!) and provide appropriate designs for them. So these designs can (and I know should) be overridden in schools. Presumably an employer can do that for Document T particularly as 1% of the population have epilepsy, diabetes is on the increase, there are heart attacks and also strokes at an average of 1 every 5 minutes in the UK.
I would suggest to your employer that the single sex toilets stay single sex with the door gaps for safety reasons and to comply with the Equality Act (2010) for sex, disability, age (frailty) and religious reasons. Unisex toilets that are enclosed and self contained - the Universal design - should be monitored regularly (and I think are not as suitable as single sex toilets because they are less safe).