UK regulations require that there is a method of switching off all lighting circuits, be it in the same or immediately adjacent room, be it an adjacent fuse board, or a physical light switch.
The isolating light switch can be what I call a ‘fish key’, typically used for testing emergency lighting circuits, but it must still be in the same or an immediately adjacent room.
Unfortunately the double relay option I posted the other day, linked to by @JDRoberts above, won’t meet regulations either… that advice was given for a second switch position, not the primary one. Also, that relay method won’t give you scenes or dimming… just on/off control, with large delays and unreliability at that!
You could theoretically use a Fibaro dimmer 2 module. They allow for two switch inputs per module, switch one controls the load, switch 2 can be used just for sending scene ID’s via single, double, triple click and hold / release events, thus programmatically controlling your smart bulbs.
You would need to power the load via the dimmer module, connect switch 1 to a ‘fish key’ to allow for isolation of the load, disable the dimming capability via the parameter settings (to avoid damage to the smart bulb), and use the switch 2 terminals with a retractive / momentary switch for scene control.
Grid systems like MK would be perfect for this, take a double gang face plate and install a fish key switch and retractive switch side-by-side.
They also come in different gang combinations… but they are certainly not the most attractive of switches.
One problem you will face is the initial calibration of the dimmer modules, as when they first power up the dimming level fades up and down a few times which could damage a smart bulb, this is automatic and unavoidable! Dimming can be disabled thereafter but not in the first instance. You would need to calibrate with regular LED bulb(s) of the same wattage, and then swap over to the smart bulbs after disabling the dim function, manual fine tuning of the calibration would probably still be required via parameter settings.
Another problem will be if you have a traditional 2 wire system at the switch? In a 2 wire install the Fibaro Dimmers draw a tiny amount of power through the bulb, which won’t work for with a smart bulb. You would need to install Fibaro bypass modules at additional cost (£9 per circuit). If you have a neutral at the switch, this won’t be an issue.
Whilst I appreciable you have already invested in smart bulbs… you are now looking to spend the same again, probably more, to double up with less function and more complexity and 100% reliance on the cloud… why not just sell the smart bulbs on eBay / gift to friends / relatives. Buy smart modules and use them as they are intended, to switch the load directly, instantly and locally.
Like you my first foray into home automation many years ago was with a stack of Wemo smart bulbs… a huge mistake which I came to regret… I compounded the problem by buying a stack of Wemo wall switches but I eventually bit the bullet and sold them all on eBay, for an ok return. I upgraded to a proper ST system using Fibaro dimmers throughout, and life is great.
The only place I still use smart bulbs are in roof spaces, triggered by contact sensors on loft hatches, but to be honest I could just as easily use dumb door switches to achieve the same thing.