I love the detolf and would really like one! It is a bit less deep than some cages, it's true, but does give a lot of scope for enrichment. If you google "Hamster detolf" and click on "Images" you will see lots of examples of how it can work. The inner bars aren't an issue - unless you end up with a particularly chewy Syrian in the future.
There are actually lots of alternatives for larger cages. Many people get cages from Zooplus which are large and reasonably priced. They also sell tank style cages like the Living World Green Eco Habitat (at a price!). It can be a bit of a minefield thinking of upgrades and working out the costs, as sometimes diy cages can work out quite expensive as well, especially when you start buying plexiglass.
I think tank style sounds like a good way to go if you are thinking of something suitable for both a Syrian or a robo. I personally would have no problems with having a Syrian in a detolf and many people do. If you have a slight concern about the inner bars though, it might be an idea to think about other alternatives.
I had thought of making a diy cage from two of the large (115cm) Ikea Lack coffee tables (as someone on here did once). With two of them (eg one fixed on top of the other one) - you automatically have a top, bottom and four corner struts, plus storage space underneath the bottom one. I reckon you could use the unused shelf from the table as a back panel, mesh the two sides, and have plexiglass sliding doors at the front. I think that's the tricky bit! Making plexiglass sliding doors, and a plexiglass internal panel behind them so the substrate doesn't fall out. Alternatively you could leave the top off and make a hinged lid from wood and mesh and just have a plexiglass panel in the front.
If it was me - a diy cage would never get done/finished and would drive me bonkers - but some people enjoy doing them
LACK Coffee table White 118x78 cm - IKEA
You would end up with a cage approximately 105cm by 70cm (allowing for the thickness of the legs) but it would only be about 40cm tall - fine for a Robo and just about tall enough for a Syrian, but it does limit the depth of substrate you can put in, which is one of the advantages of a tank style or diy cage usually.
The detolf is a lot less hassle - just needs a lid making - and does look good!
Here's the link to Zooplus. I have the Barney cage for our Syrian, which has 7mm bar spacing. If it was for a robo it would need a full level in it really (ie a shelf that creates a whole level in the cage so they can't fall from the roof). For a robo a tank style is probably a safer option though, as although 7mm bar spacing is small enough they could potentially get a leg stuck in the bars and get injured.
The Eco Habitat is great. The lid would need meshing as the slots on top are 2cm wide - fine for guinea pigs but not for hamsters. However most people plastikote the wood parts and put some kind of waterproof liner on the base. I diy cage might be sturdier and last longer though.
Not all the cages on here are big enough. But they have a good selection of 80cm, 100cm and bigger cages.
Hamster Cages | great selection at zooplus
The Marrakesch tank style one is good for a Robo but a bit limited for a Syrian in my opinion - it's quite low and not particularly deep and about 90cm internally. Also a bit expensive. But has a hinged meshed lid and the wood parts are already waterproofed. Personally, in our house, I would worry about glass breaking!
If I had a robo I would go for the Marrakesch or the detolf. If I had a Syrian I would go for a detolf or a Barney, Alexander or Savic Hamster Plaza cage. The Savic Hamster Plaza is a great cage for a Syrian and has a big front opening door. But not suitable for a robo really.
I think you would be fine going for a detolf if you want something that is futureproof for any hamster. In the rare event that you got a Syrian who chewed the bars or wood ends in the detolf, you could mesh the ends internally and take the bars out and silicone the glass together.
Stinker sounds adorable! How old is he? Robos can live a bit longer than other species, if healthy. They are notoriously hard to tame, especially if he isn't young, but very entertaining to watch. Not impossible to tame though.
Another option that could be suitable for either a Robo or a Syrian is the Ferplast Maxi Duna multy. It's a perspex tank style cage. The lid has narrow bar spacing. No diy needed. It's about £80. It's a lovely cage. Similar size to the Marrakesch internally. Although the corners slope it is deeper. Porton Aquapet charge postage on top which makes it nearer £90 I think.
Cage Maxi Duna Multy
Amazon prices vary between £80 and £90 depending what day it is!
https://www.amazon.co.uk/d/Cages-Pen...axi+duna+multy
Here are some examples of set ups in that
https://www.google.co.uk/search?q=ma...w=1366&bih=608
You can, of course, go much bigger with a diy cage if you wanted. Space is good, but they do need lots of "overhead cover" as well and not too much open empty space - so large tunnels, different levels and plenty of hidey places are good.