Well I have been around various loops in trying to come to a decision... I think the biggest thing is the price of affordable FE Glass that are not compromised in some way.
I shall share what I have read as might be helpful to others in a similar situation.Sigma Adaptor
Regarding the Sigma adaptor; there are mixed feelings on the Web about this. I think generally for supported Sigma lenses it works well, but there are some issues. The lenses apparently changes the aperture to focus, so you can here the aperture clicking noises if shooting video. AF speed is OK, but slower than native lenses. Some unsupported Canon lenses work well, others not at all. A bit of a hit and miss.Sony EA3/EA4 Adaptor
It occurred to me that most of the Sigma lenses that the Sigma adaptor supports, also come in A Mount. The EA3/EA4 adaptor supports all Sigma lenses, all Sony lenses, most Minolta lenses, all Tamron lenses, all Tokina lenses....
AF Speed on the EA3 is similar or a bit slower than native lenses, which sounds similar to the Sigma. With the EA4 adaptor, you get improved PDAF so focusing is actually faster (more like a traditional DSLR). The downside is that there are less A Mount lenses than Canon, but not all are supported anyway. EA4 is a bit bulky on the A7, but if tht was an issue you could get the EA3.
I looked at the Zeiss branded FE glass (not Sony branded Zeiss), which although are cheaper in many cases compared to the Sony, they are still expensive. They are also not as fast.
The cheapest I could get a 50/1.8 and 85/1.8 secondhand was £500 + £900 (£1400), and I really wanted 1.4s.
In looking at the various glass out there, there are no small 85/1.4s due to physics. I also want to start using the camera more, meaning I want to carry it around more.
So I have come to a temporary solution until such a time I either win the lottery or FE lenses come down in price. Seems like a backwards step, but I have bought.
* LA-EA4 Adaptor £195
* Sony 50/1.4 £150
* Minolta 85/1.4 G £490
Total of £835 for f1.4 glass, considerably cheaper than FE 1.8.
And for when I want a point and shoot, I have bought a 16-50 APS-C pancake lens. I get it it's a FF camera and I'm attaching a cheapish kit lens, and I'm back down to 10MP when using it, but the point is, it's small and manageable... so hopefully will carry it more.
But I do find it funny how a few years ago I had an a900 with Sony Zeiss 85/1.4 glass, where as now the body has moved forward to Mirrorless, but the glass backwards to legacy Minolta glass