I agree its still possible albeit - at least on higher difficultlies - in an altered form. In situations with no mids (and I have stopped chopping it out on sans-stone starts the way I sometimes did in my strict SE days) there is still often potential, given enough food and non-cottage commerce, for a strong SE even if it is a bit of a hybrid. I think that without mids (and often even with them) your long term planning should include a transition to a more cottage reliant system, gradually phasing down to your 1-2 best GP farms.
This type of strategy can be formulated in a number of ways, depending on geography, diplo situation, etc.
Just a few ideas:
-I would still consider running two scientists in every city that can support them at some early point to keep tech afloat. These cities can be transitioned to cottage cities or production cities when it is expedient. Using specialists instead of early cottages trades long term gain for a short term leverage, even without Rep.
-Maximize trade routes to give yourself some financial breathing room. Some combination of good scouting, currency, the GLH and/or ToA, good diplo, harbors, etc. (Btw, this stuff can and should be done on CE as well of course, I'm just talking about prioritization.)
-Captured territory often makes great cottage land even if your early core cities are still more SE oriented. Let the AIs work those cottages for you.
- A lot of an SEs strength is not the beakers or gold or whatever they produce, but the extra GPs they produce. It is important to manage their creation a lot more than just "pile as many GPPs into a city from as many different sources and hope I don't get a GArtist."
The extra GPs, especially if micromanaged to produce certain ones, can be employed in a lot of different ways. I won't go into them all here but I suggest you keep your bulb list close at hand. Heres one if you need it.
I hope this helps but I want to reiterate that I am no longer of the opinion that a super strict SE is optimal without the mids except in some rare cases, though I'm sure Obsolete would have something to say about that.