Regards the dingy, stowage is the pain, I use a tyre inflator connected to a diving regulator first stage and a small dive bottle to inflate my 'rubber duck' ... you take off the 2nd stage of the regulator (the bit you poke in yer mouth!) and replace it with the inflator, its inflates very very quickly compared to pumping and (big bonus) there's no huffing and puffing on a foot pump.... you can pick up an old set of regulators , bottle and the inflator very cheaply on e-bay and to be safe your local dive shop can check it over for a few pounds (what makes you think I used to be a PADI instructor?: or "Put Another Dollar In" hmmmm?!)
.....but if you do intend to make one: an easy, light contsruction is using thin plywood with the "stitch and glue" method...I used cable ties for the "stitching" and epoxy to glue the joins, the seat and gunnel (again plywood) once hard the ties can be removed (I left them in!), beef up the joints inside with epoxy filler 'fillets', a good rub down and a dollop of paint, bingo !! : its a bit like macrame?! but simple , strong and very satisfying... in true Junk tradition me thinks!
Finally the anchor, I had a very similar problem, I lost my steering in the middle of Portsmouth harbour with a gert great ferry ploughing down on me... after that salutory experience I put the anchor in cockpit, but I found it to be big, bulky, it fills the locker and cockpit with mud, a real pain! ... So, I am going to put the beastie back in in the bow locker and get another reletively small danforth with a chain (etc) just for emergencies, the idea being that I can deploy it quickly and hold while I go to the bow to release the big-un.... some sage told me a good yardstick is one pound of anchor/chain per foot length ... thoughts? PS i'm going to use a danforth as it folds easilly?